Intrauterine development of a child: periods and stages with photos. Intrauterine development of a child by month. Intrauterine development and child growth by week
The way the fetus develops over the weeks is a real miracle. In just 38-40 calendar weeks, an embryo of several cells, similar to a bunch of grapes, becomes a baby with a very complex body structure. Immediately after giving birth, he begins to use a whole arsenal of skills and reflexes, quickly adapting to new living conditions. Our article contains a brief description of the child’s development day by day from the very moment of conception, a photo of the embryo and features of different months of pregnancy.
Human embryo in the first trimester
The first trimester is the most important and difficult stage in the development of a human embryo. It is at this time that the rudiments of its organs are laid, the nervous and other systems are formed. This period is associated with a large number of risks and requires the expectant mother to pay special attention to her health and lifestyle.
Embryo growth by week in 1st month of pregnancy
It is not without reason that the first month is considered one of the most important and exciting, because right now a new life is being born. At the beginning, his pregnancy has not yet actually occurred, but the body of the expectant mother is preparing for it, regulating hormonal levels and the functioning of the organs of the reproductive system. All this is necessary not only for conception, but also for normal implantation of the embryo in the uterus and the start of its development.
First trimester - beginning of pregnancy
1-2 week
From the 1st to the 14th day of the new menstrual cycle, the follicle matures in the ovaries, from which the egg is released. It travels down the fallopian tube and meets a sperm, one of the nearly 900 million that enter the vagina. After fertilization, the morula embryo “descends” into the uterine cavity and the endometrium is implanted - approximately on days 12-17 of the cycle. At this point the actual pregnancy begins.
3 week
The fertilized egg continues to divide and grow into the wall of the uterus with lining cells. In parallel with this, the formation of the placenta and umbilical cord begins - organs vital for the development of the fetus, through which it will receive nutrients. Now the embryo consists of more than 100 cells.
4 week
At this time, the first “breakthrough” occurs in the child’s development: the formation of all systems of the baby’s future body begins. A particularly important stage is the formation of the neural tube, from which the brain and the entire nervous system are subsequently formed. The embryo grows to the size of a poppy seed with a diameter of less than 1.5 mm, from which time it is called an embryo. It is intensively implanted into the endometrium, which affects the level of the hCG hormone. It is at 4 weeks that a woman may notice a delay in menstruation and early signs of pregnancy.
Development of a human embryo at 4 weeks of gestation
Embryo development at 2 months
In the second month of pregnancy, fetal development continues every week and is accompanied by significant changes in the structure of its body. During these 4 weeks, the umbilical cord, neural tube, rudiments of limbs and fingers will form, the face will become even more proportional, and internal organs will differentiate.
5 week
The fifth week is the transition period between 1 and 2 months of pregnancy. Now the embryo has a conventional coccygeal-parietal size of up to 2.5 mm and a weight of about 0.4 g. The body's systems are rapidly developing: the neural tube is improving, future parts of the brain, lungs, stomach, trachea are being distinguished, blood vessels are growing.
week 6
The embryo grows from 3 to 6 mm, it looks like a fry, because... limbs are not yet developed. The placenta begins to form from the chorionic villi, and hemispheres appear in the brain. The small heart, in which division into chambers occurs, is already contracting, driving through blood enriched with oxygen and nutrients for the construction of the body.
week 7
The embryo at this week of development is 13-15 cm long, more than half of the “growth” occurs in the head. Its body still has an arched shape, with a “tail” remaining on the pelvic part. On the upper limbs, which are ahead of the lower limbs in formation, the hand and fingers are drawn.
8 week
The size of the embryo increases to 20 mm - the baby grows almost 2 times in just a couple of weeks. He has a brain with two hemispheres and several sections, lung rudiments, a heart, and a digestive system. The face is becoming more and more like a “human” - the eyes, ears, nose and lips, covered by eyelids, are clearly distinguishable.
Photo: what an embryo looks like at 8 weeks of pregnancy
How the fetus develops week by week at 3 months
At this stage of development of the human embryo, its length doubles, with a third of the growth occurring in the head. Gradually, the proportions will change, and now the baby begins to move his arms and legs, foci of ossification appear in the cartilaginous rudiments of the skeleton, the skin becomes less transparent, and is divided into layers in which the rudiments of hair follicles are formed.
Week 9
The ninth week is the transition from the second to the third month of pregnancy. During this time, the child's development day by day will be accompanied by a rapid increase in height from 22 mm at the beginning to 31 mm at the end. The baby’s heart beats at a speed of 150 beats per minute, and the musculoskeletal system improves. The embryo's head is pressed tightly to the chest and appears disproportionately large relative to the body and limbs.
10 week
By the end of this week, the baby will have grown to 35-40 mm according to the CTE, most of the time he will be in a half-bent state. The way the embryo looks also changes: the “tail” disappears, and buttocks form in its place. The baby floats freely inside the uterus and, touching its walls, pushes off with his feet or hands.
11 week
More than 250 thousand new neurons are formed every minute in the embryonic brain. The baby begins to develop the rudiments of baby teeth and nails. His limbs are bent, but the child regularly makes spontaneous movements with them, clenching and unclenching his fists. The iris forms in the eyes.
12 week
The most important event of this week of embryo development is the beginning of the active functioning of the placenta, which protects and nourishes the fetus. Thanks to it, the baby will receive air and all the necessary substances for the growth and construction of his own body.
Embryo development at the end of the first trimester
Stages of embryo development in the 2nd trimester
In the second trimester of pregnancy, all organs are already laid down, they begin to grow and function. During this period, fetal development is “directed” towards rapid growth and improvement of body systems.
How the embryo changes day by day at 4 months
In the fourth month, the way the fetus looks is constantly changing: every day it looks more and more like a human embryo, the limbs gradually lengthen, the head and torso will be more proportional by the middle of the trimester. The baby’s organs are actively developing, forming different body systems.
Week 13
This week of pregnancy is a transition week between the first and second trimester, when, as a rule, the first scheduled screening is prescribed. It is necessary to assess the development of the embryo day by day and exclude pathologies. By this time, the baby has a height of 6.5 to 8 cm and a weight of up to 14 g. The limbs, body and head become more proportional. The musculoskeletal system is actively being built, and the jaw already has the rudiments of 20 teeth.
Week 14
Now the baby receives all its nutrition through the placenta and umbilical cord. It grows up to 8-9 cm, a chin and cheeks are visible on its face, and the first colorless hairs appear on its head. The kidneys begin to secrete urine into the amniotic fluid. In girls, the ovaries move into the pelvis; in boys, the prostate gland begins to form.
Week 15
What does the fetus look like on days 99-105 of development? His proportions are approaching normal, CTE increases to 10 cm, and weight - up to 70-75 g. All parts of the face are formed, eyebrows and eyelids can be distinguished, the ears acquire a characteristic shape and relief.
Week 16
The baby's CTE reaches almost 12 cm, and his weight is 100 g by the end of the week. The development of the embryo day by day at this stage is impressive: all its organs are already formed, the heart and kidneys are actively working. The structure of the facial muscles improves, thanks to which the child begins to grimace.
Baby after 16 weeks of pregnancy
Pregnancy in the 5th month: how the embryo develops by day
At the 5th month, the baby is growing rapidly, all his organs are gradually getting involved, different systems of the body are being improved and coordinated. In particular, the baby’s movements become more coordinated, and thanks to the increased weight of the fetus, the expectant mother will be able to feel the first movements.
Week 17
The fetus grows up to 12 cm according to the CTE and already weighs about 140 g. This week, the baby’s own immunity comes into play, which, together with the placenta, will protect him from the negative effects of external factors. Thin skin becomes covered with vernix, and subcutaneous fat begins to accumulate under it.
Week 18
By the beginning of the week, the baby’s CTE is more than 14 cm, and his weight is from 140 to 200 g. How does the fetus develop day by day? First of all, its proportions change: the limbs grow faster than the head. The hearing aid is active, the child reacts to sharp and loud sounds. The structure of the brain becomes more complex, the transmission of nerve impulses improves, thanks to which movements become more coordinated.
Week 19
The CTE of the fetus increases from 15.3 to 19-20 cm, the weight is on average 240 g. The baby's skin is covered with lanugo fluff. The bronchial tree grows. The reproductive and thyroid glands begin to produce hormones. The entire body is protected by thick vernix lubricant.
Week 20
The development of the fetus by day of this week is associated with changes in its appearance and the coordinated work of different systems of its body. Due to lanugo and the gradual accumulation of subcutaneous fat, the baby's skin becomes less transparent. More than 25 liters of blood passes through the heart per day.
Fetal development by week at 5 months
6th month: how does the human embryo change?
In the sixth month, the structure of the baby’s brain improves. The length of the body and limbs and the size of the head become proportional, and the overall appearance is the same as that of a newborn. Interestingly, by this time the child already has a unique pattern on the pads of his fingers.
21 weeks
By the end of this week, the baby grows to 26.7 cm and weighs about 300 g. His movements are clearly felt, and the child’s daily routine can be traced by his movements. What changes occur in fetal development? Its digestive and excretory systems are trained, acid appears in the stomach, and taste perception is improved.
Week 22
The child’s CTE increases to 28 cm, the weight is already more than 400 g. The volume of subcutaneous fat increases, due to which the fetus becomes more and more like a newborn every day. Thanks to the rapid development of the brain and nervous system, the baby begins to “explore” the surrounding space - he pulls the umbilical cord, evaluates the taste of amniotic fluid, reacts to changes in lighting and different sounds.
Week 23
The baby's height from heels to crown exceeds 29 cm, weight reaches 500 g. How is the fetus developing this week? From the second month, his brain has increased 40 times, reactions to stimuli and movements become logical and coordinated. According to some studies, the child begins to dream.
Week 24
At this stage, the baby grows to 30-32 cm and weighs about 530 g. A surfactant lubricant appears in the lungs, which is necessary for protection during breathing. The cerebral cortex becomes covered with new grooves and convolutions. Subcutaneous fat accumulates more actively.
What does a fetus look like at 6 full months?
Position and development of the fetus at 7 months
In the last month of the second trimester, the baby's skin smooths out, becomes denser and gradually acquires a lighter shade. Subcutaneous fat, vital for normal thermoregulation, accumulates underneath it more and more quickly. The child opens his eyelids more often, exploring the surrounding space and reacting to bright light.
Week 25
The height from crown to heels is about 34.5 cm, and the weight increases to 700 g. The facial features are fully formed. The bone marrow takes over the function of hematopoiesis. Alveoli develop in the lungs - bubbles that will open after the baby's first breath.
Week 26
At this stage, the size of the fetus changes slightly more slowly by day than in previous months. The baby's height is about 35 cm, and his weight is 760-850 g. All systems of his body are “trained” and prepared for work outside the womb. Thanks to the coordinated work of the brain and adrenal cortex, the synthesis of new hormones begins.
Week 27
By this time, the child has gained another 1 cm in height and already weighs about 900 g. He gradually accumulates subcutaneous fatty tissue. The hair on your head, eyelashes and eyebrows may become slightly darker. The organism becomes more and more viable, i.e. even in the case of premature birth, the chances of preserving the life and health of the baby increase.
Week 28
The development of the child by the end of the 7th month allows him to survive even outside the mother’s womb in the absence of pathologies in the structure of the organs. He gains enough subcutaneous fat, although for normal independent thermoregulation its volume must increase significantly. At this time, the hemispheres of the brain work more actively; it is already known whether the baby will be right-handed or left-handed.
After 7 months, the baby begins to gain subcutaneous fat
Embryo development by week in the 3rd trimester
The last trimester of pregnancy is a time of active accumulation of subcutaneous fat, improvement and coordination of the functioning of body systems. All this is necessary to prepare the child for childbirth and life outside the womb. How does the fetus develop over the weeks?
Fetus at 8 months gestation
In the eighth month, the baby quickly gains weight and continues to grow. His skeletal and muscular systems become stronger. The lungs are preparing for breathing, the diaphragm is constantly “training”. The brain is already fully formed, but its structure and functioning are constantly being improved.
Week 29
There is less and less space in the uterus, because the child grows up to 38 cm in height and already weighs more than 1 kg. Because of this, its tremors become more noticeable and can cause discomfort for the expectant mother. All systems of his body are actively working, in particular, the kidneys excrete almost 500 ml of urine per day into the amniotic fluid.
Week 30
How does the fetus develop day by day? First of all, he very quickly accumulates subcutaneous fat, which is why his weight increases to 1.3 kg. The skeletal system becomes stronger, the limbs lengthen, the height from crown to heels is more than 39 cm. The skin brightens, folds are gradually smoothed out. The lungs actively produce a protective lubricant called surfactant.
31 weeks
This week the child already weighs more than 1.5 kg and grows up to 40 cm. By his activity, you can track his sleep and wakefulness patterns, as well as reactions to external conditions - noise, bright light, lack of fresh air, uncomfortable position of the mother. The eyes are fully formed, the color of the iris is the same in most babies, it will change after birth within three years.
Week 32
The child's height is 42 cm, weight is about 1.7-1.8 kg. The development of the fetus day by day is aimed at preparing its body for independent functioning. To do this, the recruitment of subcutaneous tissue is accelerated, the respiratory and sucking reflexes are constantly trained, digestion and blood supply are improved. The work of the excretory, nervous and endocrine systems becomes more complicated.
Fetal development at 8 months: the baby already looks like a newborn
9th month: what does the baby look like and develop?
The ninth month of pregnancy is considered by many to be the “finish line.” Indeed, the development of the child by this time makes him viable: the baby will be able to suck milk independently, and the risks of problems with breathing and thermoregulation decrease every day.
Week 33
The child grows to 44 cm and already weighs about 2 kg. He feels cramped, which is why even slight movements are clearly felt. At this time, the baby takes its final position in the uterus - head or feet down. At week 33, the size of the heart increases, the tone of blood vessels increases, and the formation of alveoli in the lungs is almost complete.
34 week
The baby's height increases by another 1 cm, while the weight gain due to the gain of subcutaneous fat can amount to almost 500 g. The baby's musculoskeletal system is strengthened. The bones of the skull are still soft and mobile - this is necessary for passage through the birth canal. Hair on the scalp grows faster and may change color.
Week 35
On average, height from heels to crown is 45 cm, and weight is from 2.2 to 2.7 kg. The child looks well-fed and accumulates more and more subcutaneous fat every day. The nail plates are clearly visible on his fingers, and the lanugo hair becomes slightly smaller.
Week 36
The height and weight of babies at this stage can vary widely. The body length is from 46 to 48 cm, and the weight is from 2 to 3 kg. The child's skin becomes smooth and bright, the number of folds decreases. All his organs are ready to work, and the body becomes completely viable.
Baby development by the end of the 9th month: the baby is ready for birth
Child development in the last weeks of pregnancy
The 10th month of pregnancy is an exciting time: labor can begin any day. The development of the child by this time makes him completely viable, and there are no longer any risks to his health during delivery.
Week 37
The baby grows to 49 cm. Every day he gains about 14 g. His appearance will not change before birth. The cartilage in the nose and ears gradually strengthens. The lungs are ripe, the alveoli, protected by surfactant lubricant, are ready for the first breath. The intestines perform periodic contractions to prepare for full peristalsis.
Week 38
The fetus looks exactly like a newborn. His body is fully formed and ready to function. The baby takes its final position in the uterus and rests its head against its base. The bones of the skull are still mobile: thanks to this, the child will be able to pass through the birth canal.
Week 39
The baby gains 20-25 g per knock, his height can vary from 50 to 55 cm. He “sinks” into the pelvis and begins to put pressure on its bones. The limbs, body length and head dimensions are completely proportional. All senses are well developed.
week 40
By this time, the development of the fetus is completed - it is ready for birth, has all the necessary reflexes to maintain health and nutrition. This week, the placenta gradually ages, and hormonal changes in the woman’s body trigger the natural process of childbirth.
Periods of childhood.
Child education
Age periods are life periods of time within which the process of growth and development, as well as the morphofunctional characteristics of the organism, are identical. When characterizing each age period of childhood, the laws of growth and development are assessed; morphofunctional state of organs and systems; features of the central nervous system (CNS), neuropsychic development; leading lines of development; features of the endocrine system; immunological features; the basic nature of the pathology characteristic of a given age period; infectious pathogens; the most unfavorable factors affecting the child’s body; creating conditions for harmonious development, taking into account the age and principles of raising children. Thus, the identification of separate age periods contributes to a differentiated approach to the child.
In the process of development of the fetus and child, there are also critical periods in relation to growth and development, maturation and formation of the functions of organs and systems.
According to the International Convention on the Rights of the Child, 1999, children are defined as human individuals between birth and 18 years of age. The following age periods are distinguished:
I. Prenatal period - from the moment of conception to the birth of the child. It lasts 280 days (10 lunar months), starting from the first day of a woman’s last menstrual cycle.
II. The neonatal period is from the moment of umbilical cord ligation to the 28th day of life. Within it, they are distinguished: early neonatal period - until the end of the 7th day (168 hours in total); late neonatal period - from the 8th to the 28th day of a newborn’s life; perinatal period - from the 24th week of pregnancy until the end of the first week after birth.
According to the recommendation of WHO experts (1960), it was calculated from 28 weeks of intrauterine development until the end of the first week after birth. Currently, the perinatal period is calculated from the 24th week of pregnancy, since studies have shown that from 23-24 weeks of gestational age the child is viable extrauterinely with the improvement of modern methods of caring for premature newborns.
III. The period of infancy is from the 29th day of a child’s life to 1 year.
IV. The period of early childhood is from 1 year to 3 years.
V. Preschool period - from 3 to 7 years.
VI. The period of primary school age is from 7 to 11 years.
VII. The period of high school age is from 12 to 17-18 years.
Prenatal period
The intrauterine period is the most important period that determines the biological fate of the human body for subsequent years, health status, adaptive reactions, and the risk of developing diseases. Currently, we can talk about the increasing importance of deviations in fetal health on the formation of human diseases. Hence the great importance of perinatal diagnosis, and the fetus acts as a patient. To directly assess the study of the functional state of the fetus, a biophysical profile, monitoring of fetal cardiac activity, and study of uteroplacental and fetoplacental blood flow are used; synchronous study of computer intervalogram of mother and fetus.
The definition of the biophysical profile includes fetal sucking movements, swallowing, sleep and purposeful movements, reflexes.
Characterized by rapid growth and tissue differentiation of the fetus. At 8 weeks, the rudiments of all major organs and systems are formed. From the 4th week, the embryo’s heartbeat is detected, at the 8th week a muscle reaction in response to stimulation is observed, by the 9th week the palms and soles become reflexogenic, and spontaneous intestinal motility is noted. The fetal circulatory system reaches its final development between 8 and 12 weeks of pregnancy. By 12 weeks, the cerebral cortex is determined. By 13–14 weeks, smooth movements appear in response to stimulation of various zones. At week 14, swallowing movements begin. By the 17th week, the grasping reflex appears. At the 18th week, respiratory movements are noted. From the 20th to the 28th week, bone marrow hematopoiesis is established (instead of liver hematopoiesis). From 28–29 weeks the fetus can actively suckle.
By the end of the second trimester of pregnancy, the fetal weight is 1000 g, and the body length is 35 cm, and by the end of pregnancy the body weight is 3200–3500 g, the body length is 48–50 cm or more.
Critical periods for growth and development:
the first 7–9 days are the period of egg implantation;
3–12 weeks - early fetal period - intensive growth and tissue differentiation of the fetus;
after 28 weeks and before the onset of labor - the late fetal period, when exceptionally rapid growth and accumulation of cell mass are noted; the processes of deposition of many nutritional components are ensured: depot of calcium salts, iron, fluorine, copper, vitamins D and B12. During this same period, surfactant matures in the respiratory organs. At this time, there is a high level of passive immunity, maturation of enzyme systems, and nonspecific factors of the body’s defense.
Fetal development is determined by the mother-placenta-fetus functional system; these are nervous, humoral, immune connections (direct and reverse).
The main factors determining and regulating fetal growth are uterine blood flow and placental perfusion. Insulin and pituitary hormones play a special role. One of the main factors ensuring normal development and growth of the body before birth is hemodynamic processes in the functional system mother-placenta-fetus. Using a Doppler study, the fetal heartbeat can be determined from 10–12 weeks of pregnancy.
Features of the fetal central nervous system. The rate of brain growth up to the 33rd week exceeds the rate of growth of other systems and organs, especially the rapid increase in brain mass in the last weeks before birth. Maturation of the cerebral cortex occurs between 12 and 16 weeks. At the 12th week, the time of appearance of electrical impulses in the respiratory centers in response to external stimuli is noted. From the 13th–14th week, smooth graceful movements of the fetus are recorded in response to stimulation of all zones with the exception of the areas of the back, occiput, and crown. From the 17th week, grasping reflexes of the hands are formed and well developed. By 27 weeks, the influence of the mother’s motor activity and emotions on the fetus was recorded. By the 28th week, the motor-cardiac reflex matures in the fetus, and by the 32nd week, the fetal reaction to sound transmitted through the abdominal wall by a change in pulse rate is recorded.
The critical period of brain maturation is the time of appearance of electrical shifts in the cerebral cortex and its responses to external stimuli - weeks 12–16.
The electroencephalogram of the fetus from 5 months has the same type and intermittent character. From 7 months, interzonal differentiation is observed. From 8 months, the EEG becomes continuous, and then qualitative differences between sleep and wakefulness appear.
Regulation of fetal motor skills and posture. The main significance of the spinal level of reflex activity is to ensure fetal posture. From the 9th week, impulses from skeletal muscle receptors were noted. From the 20th to the 40th week there is a rapid increase in the cerebellum (12 times), regulation of motor skills and posture. The cerebellar cortex is directly involved in the regulation of the general level of activity of the fetus, spatial orientation, modulation of the autonomic nervous system, ensuring adaptive behavior in the external environment of the newborn.
Features of the fetal endocrine system. There is a predominance of adrenal function. The cortical zone of the adrenal glands is very wide, the zona fasciculata is not clearly expressed; the adrenal medulla is not detected - this is the so-called embryonic type. From the 25th week, the fetus produces corticosteroids from its own substrates.
Insulin is determined in the b-cells of the pancreas by the 12th week, its synthesis increases by the middle of the intrauterine period, and the concentration of insulin in the fetal blood does not differ from that in the mother’s blood.
Insulin and somatomedins, under the influence of growth hormone of the pituitary gland, determine fetal growth. The pituitary gland is formed in the embryo at the 4th week, and from the 9th–10th week traces of adrenocorticotropic hormone (ACTH) are detected. The growth hormone of the pituitary gland influences metabolism and growth through insulin-like growth factors.
By the 4th month, the thyroid gland is structurally formed, functionally active and in terms of intrathyroidal iodine metabolism does not differ from adults. The regulation of the fetal thyroid gland is carried out by the pituitary gland’s own thyroid-stimulating hormone, since the mother’s analogous hormone does not penetrate the placental barrier.
From 27 weeks, the fetus has a functional pituitary-adrenal-hypothalamus system. Thanks to this system, the fetus is able to respond to stress.
Features of fetal immunity. Passive immunity is the transfer of maternal IgG through the placenta from the 26th week. The synthesis of fetal immunoglobulins is limited and increases in the presence of antigenic stimulation. The ability to independently synthesize IgM and IgG appears from 3 months of gestation, IgM from 7 months; IgE from 11 weeks in the lungs and liver; from the 21st week - in the spleen. The first B lymphocytes appear at 7–8 weeks, and by the 14th week their number in the fetal blood reaches adult levels. The first T-lymphocytes are formed at 10–11 weeks. By the time of birth, their number is higher than that of an adult. From the 6th week, HLA antigens begin to be typed - an individual constitutional “portrait” is created.
Nonspecific factors of fetal resistance. The synthesis of lysozyme by the fetus is recorded from the 9th week; by the time of birth, the level of lysozyme exceeds the level of an adult. The content of properdin in the fetus is low and increases rapidly during the first week of the newborn’s life. The formation of the complement system in the fetus is noted at 8–15 weeks; by the time of birth, the total level of complement is 50% of its level in the mother’s blood; By the end of the first week of a child’s life, the amount of complement increases rapidly. Leukocytes throughout the fetal period and obtained from the umbilical cord blood of newborns have a low ability for phagocytosis and low mobility. The first peripheral lymph glands are formed starting from the 3rd month of gestation; their “population” with lymphoid elements occurs during the 4th month.
Lymphatic glands and formations of the gastrointestinal tract are formed after the 21st week.
Neuropsychic activity of the fetus. Works at the end of the 20th century argue in favor of the presence of a peculiar neuropsychic activity of the fetus already in the third trimester of pregnancy. The fetal auditory and vestibular systems mature structurally by the 6th month of pregnancy. It has been proven that the fetus is able to perceive especially the intonations of sounds, while more frequent repetitions of phonetic stimulation are necessary. The fetus reacts to the mother’s voice, musical melodic sounds, which is recorded by an increase in heart rate, characteristic of the motor-cardiac reflex; At the same time, positive and negative reactions to tones were noted. The fetal hypothalamus-pituitary-adrenal system mentioned above, which is capable of responding to stress, plays a role.
The most informative indicators of developmental disorders of the fetal central nervous system have been identified. The main ones are the duration of the intermediate and quiet state of the “activity-rest” cycle, the magnitude of the motor-cardiac reflex and oscillations of the fetal heart rate in the active state of the “activity-rest” cycle, as well as the characteristics of the fetal respiratory movements.
With regard to the development of the neuropsychic activity of the fetus, the mother-child system is of great importance. The impact on the fetus and its development is carried out indirectly through the body, psyche, perception, lifestyle and activities of the woman-mother, as well as through the genetic code. It is believed that acoustic stimulation to which the fetus is exposed at the end of pregnancy leaves a trace of a reaction in nerve cells, which is the basis for the development of short-term memory.
The absence of maternal feeling, its distortion or insufficiency is the most common source of stress for a child at the antenatal stage of development. Already at the stage of intrauterine development, the most important role of the mother and family in the rational development of the child is undeniable. The system of prenatal education involves the correction of the psycho-emotional state of a pregnant woman and the upbringing of a child, starting from intrauterine development.
Preventive measures. The task of active protection of the fetus is one of the most important goals during the period of intrauterine development. This goal is achieved by influencing the fetus through the mother’s body. It has been established that already from 5–5.5 months of intrauterine life, the fetus’s gustatory, auditory, vestibular, tactile and other analyzers can function, which makes it possible to begin the prenatal education of the unborn child. This is a restructuring of the family structure with a constant emphasis on the interests of the expected child, love for him and kindness.
A pregnant woman’s routine is important: adequate sleep, walks, and hygienic exercises. Physical activity and walking play a special role. The life support processes of the fetus depend on the motor activity of the pregnant woman (energy rule of skeletal muscles). A decrease in muscle activity is combined with a decrease in impulses in the central nervous system and respiratory muscles of the fetus. Creative contact between mother and father with the fetus, conversations with it, and gentle singing are necessary. It is noted that the baby's head in the womb moves behind the father's hand stroking the pregnant woman's belly. Melodic music plays a huge role. Examples of the differentiated relationship of the fetus to music in the third trimester of pregnancy are described: the music of Mozart, Vivaldi, Tchaikovsky calms the fetus; Rock music doesn't work well. The fetus is soothed by the melodious singing of the mother, as well as the singing of the parents in a duet. A pregnant woman needs to avoid television horror films and programs containing violence and cruelty. A pregnant woman should follow the recommendations for a balanced diet.
Preparing the mammary glands for lactation is of great importance.
Possible nature of the pathology in the prenatal period. Exposure to unfavorable factors in the embryonic stage (before the 8th day), especially viruses, radiation lead to chromosomal and gene abnormalities or death of the egg; in the embryonic stage (from the 8th day to 9–10 weeks) to a violation of organogenesis: deformities, congenital defects.
Maternal diseases and toxic influences (smoking, alcohol, drugs) in the embryonic stage (11–12 weeks) can lead to intrauterine growth retardation and damage to the central nervous system. When exposed to unfavorable factors in the early fetal stage (up to 28 weeks), there may be a delay in the growth and differentiation of organs and tissues: their hypo- and dysplasia; prematurity; and in the late fetal stage (after 28 weeks) - insufficient formation of depots in the fetal body: fat, protein, vitamin (D, B12) and mineral - calcium, iron, copper, selenium. During this period, there may be premature birth and functional immaturity of the fetus.
One of the most common syndromes of the perinatal period, which directly affects the physical, neuropsychic development and morbidity of the baby, is intrauterine growth retardation (IUGR). According to WHO, in European countries IUGR occurs in 6.5%, and in Central Asia - up to 31%.
In the pathology of the prenatal period, hypoxic damage to the brain plays an important role, as well as in case of malnutrition in the pregnant woman - a decrease in the number of glial cells in the brain. Particularly dangerous is a nutritional deficiency of folic acid, zinc, copper and other essential nutrients.
Exogenous toxicants, especially salts of heavy metals, leading to metabolic disorders and damage to the organs and systems of the fetus, have an adverse effect on the development of the fetus. Magnetic resonance imaging provides almost 100% accuracy in visualizing the state of the fetal central nervous system and its anomalies.
Fetopathies can be caused by hormonal disorders of the mother: diabetes mellitus, hypothyroidism, adrenal insufficiency.
One of the leading places in the formation of fetal malformations belongs to a group of infectious pathogens: rubella, cytomegaly, toxoplasmosis and herpes viruses. Testing for antibodies to rubella, cytomegalovirus and toxoplasma is mandatory.
When the fetus is infected before 5–6 months of pregnancy, a generalized process usually develops with a predominance of damage to the central nervous system, liver and kidneys. With later infection, and especially when infected immediately before birth or during childbirth, infectious diseases develop, such as pneumonia, pyelonephritis, otitis media, conjunctivitis, etc.
Children with manifestations of intrauterine infection (IUI) have prolonged jaundice, decreased muscle tone, motor activity and sucking reflex, significant initial loss of body weight and slow recovery, repeated drops in body weight, a “flat” weight curve, as well as low-grade body temperature. Tests for determining serum concentrations of C-reactive protein (CRP), interleukin-8 and prealbumin have the maximum diagnostic information value for IUI of bacterial etiology [Volodin N.N. et al., 2001]. Elevated concentrations of CRP and IL-8 in the blood serum are regarded as the presence of systemic inflammation and are the basis for starting antibacterial therapy in newborns.
Currently, prenatal diagnostics in the first and second trimesters of pregnancy, ultrasound, DNA probes, cordocentesis, amniocentesis, chorionic villus biopsy are of great importance, allowing to identify congenital malformations in 75–80% of cases, chromosomal diseases (methods of in situ hybridization with chromosome-specific DNA- probes) in 85–95%, monogenic diseases of more than 50 nosological forms (Aylamazyan E.K.), gene diseases - cystic fibrosis, hemophilia A and B, von Willebrand disease, myotonic dystrophy, Duchenne muscular dystrophy.
The fetus acts as a patient in cases of fetosurgery and hemolytic disease. The first successful attempts at treatment with fetal human brain tissues, the use of neurotransplantation of brain stem cells, were obtained. Preclinical detection and treatment of phenylketonuria, galactosemia, and hypothyroidism are of great importance. Drug correction of defects in adrenogenital syndrome, hemophilia, and diabetes is successfully carried out. Prospects - in gene therapy.
Newborn period
The newborn period is the first 28 days of a child's life, or four weeks. This is the most crucial period for a child’s adaptation to environmental conditions. It is very important, according to WHO experts, to immediately after birth carry out procedures that strengthen the bonds between mother and newborn:
place the baby on the mother's stomach;
give the newborn the mother's breast in the maternity ward;
ensure that mother and child stay together.
A distinction is made between the early neonatal period - from the moment of ligation of the umbilical cord until the end of the 7th day of life (168 hours in total) and the late neonatal period - from the 8th to the 28th day of the newborn’s life.
In the early neonatal period, the following periods of greatest tension in adaptation reactions are noted: the first 30 minutes of life - acute respiratory-hemodynamic adaptation; period from 1 to 6 hours - synchronization of the main functional systems; on the 3rd–4th day of extrauterine life - intense metabolic adaptation due to the transition to a lactotrophic type of nutrition and an anabolic type of metabolism.
In the late neonatal period, further adaptation to environmental conditions occurs. The most important criteria for a child’s well-being during this period are the dynamics of body weight and height, neuropsychic development, and sleep status. To assess physical development, the mass-height index (Quetelet 1) or the Tour index is used - the quotient of body weight in grams divided by body length in centimeters. The weight-height index for healthy newborns ranges from 50 to 60.
The average body weight of newborns is 3200–3350 g for girls, 3400–3500 g for boys, and body length is 50–51 cm.
Features of growth and development. After birth, a physiological loss of body weight occurs (by the 3rd–5th day of life) of the newborn by 6–8% of the body weight at birth, and by the 6th–7th day of life there is restoration. By the end of the first month of life, weight gain averages 600 g or 20% of body weight at birth. The increase in body length during the first month of life occurs by 3 cm. The head circumference of a newborn is 34–36 cm, the chest circumference is 32–34 cm; leg length - 36–40% of body length. Adaptation to environmental conditions, respiratory organs, blood circulation and heat production are positively influenced by the spontaneous movements of the newborn; In this regard, it is important not to limit them.
Features of the central nervous system. The weight of the newborn's brain is 10% of the total body weight. Large grooves and convolutions of the brain are well expressed, but have shallow depth. There is insufficient differentiation of the cerebral cortex and the presence of unconditioned reflex reactions. Reactions to painful stimulation are of a generalized nature. A newborn has 10 times more cold receptors than heat receptors, and therefore the child’s sensitivity to cooling is higher than to overheating. The predominance of food dominance is characteristic.
The cerebellar cortex is involved in the processing of sensory information and spatial orientation.
Within 2–3 days, the newborn has an increased level of non-opiate peptides - neurotransmitter neuroamines (neurotensin, substance P, bombensin), involved in the regulation of a number of hormones of the gastrointestinal tract, pancreas, and sympathetic-adrenal system.
A newborn has developed taste and olfactory analyzers. The taste threshold is higher than that of an adult.
During the newborn period, intensive development of the auditory and visual analyzers is observed; tactile and emotional contact with the mother. An important role is played by the presence of the newborn’s innate orientation reflex - the development of positive emotional orientation reactions from the auditory and visual analyzers.
A newborn has innate reflexes: search - the reflex of searching for the mother's breast; sucking and swallowing; prehensile. The newborn has a reflex of support on the legs and automatic walking (stepping). With a normally expressed walking reflex, the legs do not give way or cross. By 1–1.5 months of a child’s life, this reflex fades away. A reflexive turn of the head to the left or right when the child is positioned on his stomach, arms along the head. A newborn has a crawling reflex - when the palm touches the feet, the child attempts to crawl.
Features of the endocrine system of the newborn. Three successive phases of hormonal adaptation in newborns have been identified:
Phase I - the first 3 hours of a newborn’s life. It is characterized by the highest level of maternal and fetal hormones (thyroxine, triiodothyronine, thyroid-stimulating and somatotropic hormones).
Phase II - the next 3 days - there is a decrease in maternal hormones, an increase in the newborn’s own hormones.
Phase III - from the 4th to the 6th day of the newborn’s life. It is characterized by a minimal level of fetoplacental hormones, preservation of the level of pituitary hormones and a decrease in thyroid hormones.
In newborns, low biological activity of the adrenal glands is observed (80% of the adrenal cortex consists of the germinal zone). By 12–14 days of life, an increase in corticosteroid levels is observed.
The function of the thymus and thyroid glands predominates in the newborn. Transient hypofunction of the parathyroid glands is observed: early (on the 2nd–3rd day) and/or late - on the 10th day and the first weeks of life. Transient hypofunction of the parathyroid glands can manifest itself as increased neuromuscular excitability and readiness for seizures (newborn tetany). A hormonal crisis in the newborn is possible, associated with a disruption in the relationship between the endocrine apparatus of mother and child.
Features of immunity. At birth, the content of T and B cells in the child’s blood is the same as that of an adult, the level of natural killer cells is low, IgG is maternal; IgM - traces, its amount increases from the first week; Serum IgA is low, synthesis increases from the third week. By the time of birth, the absence of secretory IgA was noted, from the end of the first week - traces; IgE can be increased due to prenatal sensitization.
A feature of the newborn’s reaction to the first contact with the antigen is the absence of memory cells and their appearance after repeated contacts.
Nonspecific protective factors. The newborn has higher levels of lysozyme than the mother; by the 7th–8th day it decreases to adult levels. At the time of birth, the level of properdin in the blood is low, increases rapidly within a week and by the end of the 1st month of life does not differ from the level in adults. The level of complement components C3a and C5a is reduced, and therefore chemotaxis, opsonization and bactericidal activity are reduced (resistance to viral and bacterial infections is reduced). The production of interleukins and interferon gamma is limited. In a newborn, the absorption capacity of phagocytes is sufficiently developed, but the completed phase of phagocytosis is not perfect.
The first critical period of immunity in a child is noted - this is weak resistance to opportunistic gram-negative flora.
A newborn is characterized by a tendency to generalize the infectious process, as a result of which the frequency of septic conditions increases.
Newborns who have had or are suffering from intrauterine infection have elevated levels of IgA and IgM.
Neuropsychic development. For 1–2 hours after normal delivery, the newborn is in a state of alertness. Capable of scanning simple geometric shapes, among them preference for those more similar to a human face. During the first month of life, the child pays attention mainly to people's eyes. Inhibition processes predominate. He sleeps most of the time, but on the 2-3rd day there is anticipation of the upcoming feeding, and on the 5-7th day - hungry excitement. When feeling hungry, a “digging” reflex is observed - turning the head towards the mother’s breast nipple and “digging” movements around it, caused by a feeling of hunger or other irritants in the mouth area. At the end of the 2nd week, a reflex to the position of the newborn under the mother's breast and a reflex of visual concentration appear. It is expressed by active cognition of an adult, 2–3 minutes after suckling. A newborn develops auditory concentration by the end of the 2nd week, and visual concentration by the end of the 1st month of life. An indicator of a newborn’s perception of an object is the movements of the eyeballs, expressed in tracking and fixation of gaze.
1. The main stages of intrauterine development, their sequence and general characteristics
In intrauterine development of a person, three periods are conventionally distinguished:
· Implantation period lasts from the moment of fertilization to 2 weeks. This period is characterized by rapid systematic fragmentation of the fertilized egg, its movement along the fallopian tube to the uterine cavity; implantation (attachment of the embryo and penetration into the mucous membrane of the uterus) on the 6–7th day after fertilization and further formation of the membranes, creating the necessary conditions for the development of the embryo. They provide nutrition (trophoblast), create a liquid habitat and mechanical protection (amniotic fluid).
· Embryonic period lasts from the 3rd to 10–12th weeks of pregnancy. During this period, the rudiments of all the most important organs and systems of the future baby are formed, the torso, head, and limbs are formed. The placenta is developing - the most important organ of pregnancy, separating two bloodstreams (mother and fetus) and ensuring metabolism between mother and fetus, protecting it from infectious and other harmful factors, from the mother’s immune system. At the end of this period, the embryo becomes a fetus with a child-like configuration.
· Fetal period begins from the 3rd month of pregnancy and ends with the birth of the child. Nutrition and metabolism of the fetus is carried out through the placenta. There is rapid growth of the fetus, formation of tissues, development of organs and systems from their rudiments, formation and formation of new functional systems that ensure the life of the fetus in the womb and the child after birth.
After the 28th week of pregnancy, the fetus begins to form a supply of valuable substances necessary in the first time after birth - calcium salts, iron, copper, vitamin B12, etc. The surfactant matures, ensuring normal lung function.
Sequence of events: fertilization-zygote- (cleavage-morula-blastocyst-gastrula) - differentiation (organogenesis).
2. Explain the concepts: what is pluripotency and pluripotency, determination, morphogenesis, homeotic genes? What is the significance of cell death in embryogenesis?
Pluripotency– the ability to differentiate into all types of cells, except external embryonic tissues.
Multipotency(stem cells) - the ability of cells of living organisms to change (differentiate) in a special way (that is, to receive specialization and further develop like an ordinary cell).
Determination- this is the process of determining the path, direction, program of development of the material of embryonic rudiments with the formation of specialized tissues.
Morphogenesis– the formation of the spatial organization of the organism and its parts (the emergence and development of organs, systems and body parts of organisms both in individual, historical, or evolutionary development).
Homeotic (homeotic) genes- these are genes on which the specific development of segments, which determines the body plan, depends.
Cell death- a widespread phenomenon both in embryogenesis and in embryonic histogenesis. As a rule, in the development of the embryo and tissues, cell death occurs as apoptosis. Examples of programmed death are the death of epithelial cells in the interdigital spaces, the death of cells along the edge of the fused palatal septa. Programmed death of tail cells occurs during metamorphosis of the frog larva. These are examples of morphogenetic death. In embryonic histogenesis, cell death is also observed, for example, during the development of nervous tissue, skeletal muscle tissue, etc. These are examples of histogenetic death. In the definitive organism, lymphocytes die by apoptosis during their selection in the thymus, cells of the membranes of ovarian follicles during their selection for ovulation, etc.
3. Periods of prenatal development, their duration.
The prenatal period is the period from fertilization to birth. 30 hours after fertilization, the egg divides into two cells, and by the fifth day the embryo already has more than a hundred cells and is a hollow ball filled with liquid. After implantation, which occurs at the beginning of the second week, the growth and development of the unborn child is even more accelerated. In just a month and a half, a tiny creature is formed from a fertilized egg, which already has the rudiments of all internal and external organs and the main parts of the brain.
By the end of the second month, the intrauterine child is already quite similar to a person: he has a large rounded head with a high convex forehead, clearly visible eyes, nose, and mouth. The arms and legs are still short compared to the body, but they already have all the fingers.
The main development ends by the middle of the intrauterine period, with respiratory movements appearing from 20 weeks. By 20 weeks, all sense organs are developed and functioning, and a decisive turn has taken place in the structure of the brain: now it is different from the brain of other higher primates, our closest relatives in the animal world, and is developing like the human brain.
At 22–23 days, the heart of the embryo begins to beat, and at the same time the nervous system begins to form. At 6 weeks, all parts of the brain are present and the vestibular apparatus begins to function.
Already at 7.5 weeks, a developing child feels touch on the skin of his face, at 10 weeks he opens his mouth, at 10.5 weeks he bends his fingers, and at 11–12 weeks he can move them and clenches his fist.
By the middle of the prenatal period (at about 16 weeks), hearing sensitivity awakens.
Very early, from three months, taste sensitivity appears, and by 5 months the baby reacts to a change in the taste of amniotic fluid with a grimace of pleasure or disappointment.
The last thing to develop is vision - after all, there is nothing to see in the womb, it is almost always dark there. But there are already eye movements: at 17 weeks the baby squints his eyes, and from 6 months he reacts to the illumination of the mother’s abdominal wall with orange light.
Meiosis is a special type of cell division that results in the formation of sex cells. During meiosis, the number of chromosomes in daughter cells is halved.
The process of meiosis consists of two successive cell divisions - meiosis I (first division) and meiosis II (second division). As a result of the first division of meiosis, called reduction, cells are formed with the number of chromosomes halved. The second division of meiosis ends with the formation of germ cells.
Meiosis phases:
Prophase I - spiralization of double chromosomes, their shortening. Conjugation, the nuclear envelope disintegrates, the nucleolus disappears, and spindle filaments are formed.
Metaphase I is the location of homologous chromosomes lying in pairs in the equatorial plane of the cell. Anaphase I, during which entire homologous chromosomes, each consisting of two chromatids, move to opposite poles of the cell. Telophase I, during which two cells are formed with the number of chromosomes halved.
This is followed by the second meiotic division (meiosis II). From each initial cell four cells with a haploid set of chromosomes arise.
Biological significance of meiosis
Thanks to meiosis, mature germ cells receive a haploid (n) number of chromosomes, but upon fertilization, the diploid (2n) number characteristic of this species is restored. A complete diploid set of chromosomes and a constant amount of DNA are provided for each species. The patterns of hereditary transmission of a trait from parents to offspring - hereditary variability - are determined.
5. Sperm. Structure, functioning. Capacitation.
A mature sperm has a length of up to 50-60 microns and consists of a head, neck and tail. The head of the sperm contains a nucleus surrounded by a thin layer of protoplasm. The neck has protoplasm containing a modified centrosome, which promotes the process of fragmentation of the fertilized egg. The tail consists of protoplasm and performs motor functions. As a result of the oscillatory movements of the tail, sperm are able to make independent movements in the female reproductive tract at a speed of 2-3 mm/min. Sperm acquire the ability to move after their contact with the secretions of the seminal vesicles and prostate gland. This mixture is called seminal fluid, or sperm.
Capacitation is the process by which a sperm acquires the ability to fertilize an egg. (i.e. final maturation in the female reproductive tract).
Alavi Maria
1 .The main stages of intrauterine development, their sequence and general characteristics.
Human embryogenesis is part of his individual development, ontogenesis. It is closely related to progenesis (the formation of germ cells and early postembryonic development.
Human embryology studies the process of human development, from fertilization to birth. Human embryogenesis, which lasts an average of 280 days, is divided into three periods: initial (first week of development), embryonic (second to eighth weeks), and fetal (from the ninth week until the birth of the child).
In the process of embryogenesis, the following main stages can be distinguished:
1. Fertilization ~ fusion of female and male reproductive cells. As a result, a new unicellular zygote organism is formed.
2. Crushing. A series of rapidly successive divisions of a zygote. This stage ends with the formation of a multicellular embryo, which in humans has the form of a vesicle-blastocyst, corresponding to the blastula of other vertebrates.
3. Gastrulation. As a result of division, differentiation, interaction and movement of cells, the embryo becomes multilayered. The germ layers ectoderm, endoderm and mesoderm appear, bearing linings of various tissues and organs.
4. Histogenesis, organogenesis, systemogenesis. During the differentiation of the germ layers, tissue rudiments are formed that form the organs and systems of the human body.
2. Explain the concepts: what is pluripotency and pluripotency, determination, morphogenesis, homeotic genes? What is the significance of cell death in embryogenesis.
Pluripotency- the ability to differentiate different tissues of different germ layers.
Multipotency- the ability of the genome of adult stem cells to change the differentiation profile when transplanted into a new recipient tissue.
Determination- determination of the development path. The cellular system chooses one of many development paths.
Morphogenesis-formation of the spatial organization of the body and its parts. The cell “knows” its place and differentiates in accordance with its position. A morphogenetic field-zone is created within which cells exchange signals of positional information and differentiate, remembering their original purpose. During morphogenesis, the following occur: proliferation, intercellular interaction, induction, migration, cell death.
Homeotic genes determine the processes of growth and differentiation. Mutations in homeotic genes can cause one part of the body to change into another. Homeotic mutants are those organisms in which an organ of a different type develops in place of an organ. Homeotic genes control the work of other genes and determine the transformation of externally indistinguishable areas of the embryo or a specific organ (tissue, part of the body).
Apoptosis- programmed cell death. A natural process of mass cell death during embryonic development, histogenesis and morphogenesis. For example, fingers of the limbs are formed under the condition of apoptosis. Organisms with extensive defects caused by impaired apoptosis die in the early stages of ontogenesis. Pathological processes develop when apoptosis is suppressed or enhanced. With insufficient apoptosis, autoimmune processes and malignant neoplasms progress. With increased apoptosis, aplasia and degenerative processes occur, as well as some deformities with tissue defects.
A woman is created by nature in such a way that at least once in her life she can give the world a new person. The period of waiting and birth of a child is the brightest and at the same time alarming time. But the expectant mother should not worry unnecessarily. She should know that a normal pregnancy is the key to the proper development of her child.
If a woman has a clear idea of how the baby’s body is formed throughout pregnancy, then it will be quite easy for her to do everything necessary to avoid the development of pathologies.
Should a woman know how her child is developing?
Knowing how the intrauterine development of the fetus occurs week by week, the expectant mother can correctly organize her diet and daily routine. Also, having complete information about what changes are considered normal, a woman will avoid a state of unreasonable anxiety.
Calculating the intrauterine development of the fetus by week, it should be noted that it lasts 40 of these calendar periods. In other words, a woman’s pregnancy lasts 280 days. During this time, the child undergoes a complete process of formation and development of all organs and systems.
Gynecologists examine the intrauterine development of the fetus by week and by period, of which there are two: embryonic and fetal.
The first lasts from the moment the egg is fertilized until the 8th week of pregnancy. During this period, after fertilization, an embryo is formed, which descends into the cavity and attaches to it. The fetal period lasts from the beginning of the 9th week until the moment of birth. The embryo transforms into a fetus, develops and grows.
It is also common to divide pregnancy into trimesters:
- First trimester (1 - 12 weeks).
- Second trimester (13 - 27 weeks).
- Third trimester (28 - 40 weeks).
Now we can take a closer look at how intrauterine development of the fetus occurs week by week.
What happens during the embryonic period?
The most important thing from this period of development is the formation of the embryo. Over time, he begins to take on the shape of a person. The embryo is formed from the moment the egg is fertilized. This usually occurs in the fallopian tube.
From the moment the egg is fertilized, the development of the fetus begins.
According to the weeks of pregnancy, a morula is formed in the first seven days. It is a multicellular organism, a prototype of an embryo. The morula attaches to the wall of the uterus, and its outer cells form the umbilical cord and the outer membranes of the fetus. From the cells that are located inside it, the organs and tissues of the unborn child are formed.
How does the woman feel?
In the first week of pregnancy, a woman’s body temperature is slightly elevated, it is close to 37˚C. There are no hormonal changes in the body yet, but the expectant mother instinctively feels the changes taking place. From this moment on, a woman should be very careful about her diet and lifestyle, eliminate bad habits and follow the doctor’s recommendations.
Every expectant mother will be very interested in how the fetus develops over the weeks of pregnancy. This information will help a woman prevent many dangerous conditions. The third week of pregnancy is alarming because it is during this period that there is the greatest risk of fetal rejection. The woman's immune system tries to reject the embryo. However, in response, a special protein is released that suppresses this protective reaction, and the unborn child has a greater chance of survival.
What happens to the embryo in the first weeks of pregnancy?
This period is also characterized by the formation of the placenta. The unborn child at three weeks is a ball with a diameter of 0.2 mm. But during this period, the lungs and respiratory organs, cardiovascular system, spinal cord and brain are actively formed, and the baby’s face and gender are also formed.
The woman begins to feel mood swings, drowsiness and fatigue, and early toxicosis may occur.
Further development of the fetus (this is already the fourth week of pregnancy) occurs very intensively. The unborn child develops three germ layers:
- endoderm - the basis for the development of internal organs;
- mesoderm is what the skeleton and bones will be formed from;
- ectoderm - material for the formation of the nervous system.
The embryo already has a pulsating tube that develops into a heart. During this period, a heartbeat can be heard on an ultrasound. The respiratory organs and brain continue to form, and the face emerges more clearly. The embryo develops limbs, and by the end of the week they are already bending. The embryo is located in the placenta and maintains contact with the mother through this organ.
His heart is already beating!
During this period, many women are just learning about their pregnancy, especially if it is the first. Having found out this fact for herself, the expectant mother is interested in the main question: how does the fetus develop?
In terms of weeks of pregnancy, this is already the fifth calendar period. At this time, the embryo still bears little resemblance to a human being, but its heart already beats, its sex is clearly defined, and its kidneys, liver, pancreas and thyroid glands are formed.
Already at the 8th week, the future baby acquires the outlines of a person, his height is 3-4 cm. His arms and legs are already formed, his forehead is clearly visible, and the outlines of his eyes, lips and nose have been outlined. Internal organs are actively formed and developing. The stomach is already able to produce juice, the heart is formed, the intestines are growing, the trachea and bronchi have appeared. The spine, brain and limbs are actively developing.
By the end of the eighth week of pregnancy, the embryonic period of development ends, but the first trimester still continues. The unborn child has already acquired a human appearance, the placental-uterine blood circulation has been formed.
Fetal period
This stage begins from the 9th week of pregnancy and lasts until birth. The fetal period is divided into two parts:
- early (9 - 28 weeks);
- late (29 - 40 weeks).
During the early fetal stage, fetal development continues. In terms of weeks of pregnancy, this is the ninth. At this stage, fetal growth is 40-50 mm. He begins to show activity: bends his arms and legs, turns his head, brings his fingers to his mouth. But the mother is not yet able to feel this, the fetus is still too small.
Externally, the future baby looks like a little man with a big head. The eyes are still closed, and the skin is transparent. The genital organs begin to form, and this process will continue until the 20th week. The cerebellum and pituitary gland develop. The heart has four chambers. The tail disappears, being replaced by the tailbone.
The embryo turns into a fetus
At the tenth week of pregnancy, the embryo is already called a fetus and weighs 5 grams. His photographs already show isolated fingers, neck, elbows, knees, eyelids and upper lip.
There are taste buds on the tongue, the thickness of the umbilical cord increases.
The eleventh week of pregnancy is characterized by further development of the fetus. He already has eyelashes and baby teeth. The rectum is formed. The spinal cord is already producing red blood cells. The intestines are ready to go.
During this period, many mothers are referred by a gynecologist for a routine ultrasound. When undergoing this procedure, women are interested in the main question: is fetal development normal?
According to the weeks of pregnancy, the twelfth period begins. During this period, the child’s phalanges of fingers and earlobes are formed, he opens and closes his eyes. The intestines are already contracting, and the liver is able to secrete bile. The baby’s circulatory system is functioning, leukocytes appear.
At the twelfth week, the first trimester of pregnancy ends and the second begins.
The baby is actively growing
During this period, all fetal systems are formed, their development and growth are underway. At the thirteenth week, which marks the beginning of the second trimester, the baby reaches up to 80 mm in length and weighs about 20 g. At this time, the skeleton of the fetus is intensively formed, the pancreas begins to produce insulin.
The gynecologist will refer the expectant mother for the first genetic test. After studying the results of the ultrasound, the doctor will be able to tell you how the intrauterine development of the fetus occurs by week of pregnancy, and whether the indicators correspond to the norm.
At the 14th week, the baby’s face continues to form, facial expressions, eyebrows and hair appear on the head. On the body of the fetus, fluff and cheese-like lubricant are formed. The thyroid gland begins to work and its own hormonal levels develop.
The excretory system is functioning, the child is making breathing movements.
In the antenatal clinic, you probably saw a stand that depicted the intrauterine development of the fetus by week.
A table with this kind of information will be useful to every woman.
At the fifteenth week of pregnancy, the child develops hearing, the intestines form original feces, and the placenta thickens. The fruit weighs about 50 g, its height is 60 mm.
The expectant mother feels the baby's first movements
The sixteenth week of pregnancy is marked by an increase in the volume of amniotic fluid. The baby is actively moving, and the mother begins to feel it. The muscles on the face are developed and the child at this stage is characterized by facial expressions. The bones and nails are almost completely formed, the skin is very thin and the blood vessels are clearly visible through it.
During this period, the gynecologist refers the woman to a second genetic screening. To do this, the expectant mother will have to undergo a second ultrasound. It clearly shows the intrauterine development of the fetus week by week. Photos that can be taken at this stage are presented below.
We count fetal movements
The third trimester begins from the 28th week of pregnancy, and the late fetal period begins from the 29th week. At this time, the baby is a little cramped in the womb, and his movements are not so active. Nevertheless, the woman must clearly monitor the tremors, their number should be at least 10 per hour. The brain is actively developing, and furrows appear on it. The teeth are covered with enamel, the eyes are capable of focusing. The baby's weight is about 1250 g and height is 37 cm.
At 30 - 31 weeks of pregnancy, the baby already takes its final position in the uterus. The fetus actively gains weight by increasing muscle mass and subcutaneous fat. If a child is born during this period, he has every chance of survival.
Further intrauterine development of the child (week by week this is already the 32nd calendar period) is characterized by the improvement of the immune and nervous systems. The child has his own waking and sleeping schedule, he has his own temperament. The baby weighs 1800 g and is 42 cm tall.
At the 33rd - 34th week of pregnancy, the baby actively trains the lungs and perceives the entire environment to the fullest. The skin of the fetus becomes smooth, the bones of the skull become stronger.
Baby getting ready for birth
At 36 - 37 weeks of pregnancy, the fetus is preparing to be born. He’s already cramped in his mother’s belly and it’s becoming more and more difficult for him to move.
His body has enough fat reserves for thermoregulation after birth, his lungs are ready to breathe. There is no longer any fuzz on the body, but the hair on the head and nails are growing back.
At 38 - 40 weeks, all mothers expect childbirth. This can happen at any time. The child lowers and the mother begins to breathe easier. The woman carefully monitors the passage of the mucus plug and the appearance of contractions.
And finally, it happened! Mom and baby are now together. The baby is still very small, but full of strength to explore the new world. Now his status is a newborn.
Table of intrauterine development of the fetus by week of pregnancy
This article provides a full description of how the intrauterine development of a child occurs week by week. The table below will serve as a kind of conclusion to all of the above and will serve as a reminder for the expectant mother.
| Gestational age in weeks | Fruit length, cm | Fruit weight, g | Development of organs and systems |
| 4 | 0,1 | Fertilization of the egg, its implantation, embryo and organ rudiments. | |
| 5 | 0,15 - 0,2 | Layer of the liver, pancreas, upper respiratory organs, heart. | |
| 6 | 0,4 - 0,6 | The appearance of limb buds, hearing the heartbeat, the neural tube closes, and parts of the larynx and middle ear are formed. | |
| 7 | 0,7 - 0,9 | The trachea, esophagus, small intestine, adrenal glands and sternum develop. The brain is actively developing. | |
| 8 | 0,9 - 1,2 | The embryo has a clearly distinguishable body and head, which are equal in size. The rudiments of the nose, eyes, mouth and reproductive organs are formed. | |
| 9 | 1,3 - 1,5 | 1 | The cerebellum develops, fingers on the limbs form. |
| 10 - 11 | 2,7 - 3,5 | 4 | Joints, upper lip, ears, external genitalia, and the beginnings of baby teeth develop. |
| 12 | 9 | 20 - 25 | The face is formed, the intestines contract, the liver produces bile, the child moves. |
| 13 | 10 | 28 | The limbs are fully formed. The pancreas produces insulin. |
| 14 - 15 | 12,5 | 50 - 90 | The excretory system is active, the child produces urine. |
| 16 | 16 | 120 | Let's distinguish the sex of the fetus. The skin is very thin, muscles are forming. The child does not move so chaotically, the mother feels the first tremors. |
| 20 | 25 | 280 - 300 | There is fluff and cheese-like lubricant on the baby's skin. The intestines form original feces. The child is able to hear. |
| 24 | 30 | 600 - 800 | The work of the kidneys is activated, the fetus dynamically gains weight. |
| 28 | 35 | 1200 | The muscles and reproductive system of the child are formed. |
| 32 | 40 | 1500 - 1600 | The sensory organs and nervous system are actively developing: the baby is able to see light and feel taste. |
| 36 | 45 | 2400 - 2500 | The child quickly gains weight and his activity decreases. |
| 40 | 50-52 | 3200 - 3500 | The baby is ready to be born. |
Of course, it is best to study this information when you are just planning a pregnancy. Then a woman has a better chance of properly organizing her diet, regimen, and taking the necessary vitamins and minerals. However, information about the intrauterine development of the baby will always be timely and interesting for the expectant mother, regardless of the duration of her pregnancy.
The prenatal period is divided into 3 stages:
♦ pre-embryonic;
♦ germinal (embryonic);
♦ fetal stage.
Pre-embryonic stage
lasts 2 weeks. The birth of a human being as a result of the union of a sperm and an egg is a unique event. Only one in 300 million sperm will be able to penetrate an egg and fertilize it, determining the sex and genetic traits of the child. From this moment fertilization begins.
Over the next 24-48 hours, the egg and sperm unite into a separate cell - a zygote (from the Greek “to combine, join together”). 48 hours after fertilization, the zygote, moving along one of the fallopian tubes towards the uterus, divides into 2 cells. Then, as a result of the second fragmentation, these 2 cells are formed into 4, etc. The process of cell fragmentation accelerates, so that by the end of the 6th day more than 100 cells are formed. Each cell contains 23 chromosomes from the mother and 23 from the father, together they form the individual genetic code of the child.
As a result of cell division, they form a dense ball called morula. After about 4 days, fluid accumulates in the center of the morula and a cavity is created. This structure is called blastocyst. At first, the blastocyst floats freely in the uterus, but after a few days sponge-like protrusions form on it - chorionic villi. They penetrate the wall of the uterus and, dissolving it, become fixed in it. This process is called implantation and triggers hormonal changes that signal the start of pregnancy.
Normally, implantation is completed approximately 2 weeks after conception.
After implantation is completed, it begins embryonic period. This is a time of critical development and growth, lasting until the end of the 2nd month from the moment of conception (the term “embryo” comes from the Greek word meaning “tumor”).
During the embryonic period, two very important processes occur simultaneously. Firstly, from the outer layer of cells all those tissues and structures are formed that, during the remaining period of pregnancy, will support, nourish and protect the embryo, and later the fetus. Secondly, the development of all organs and characteristic features of the embryo itself begins from the germinal disc.
Throughout the entire 6 weeks of the embryonic period, the embryo grows rapidly.
The internal cells of the embryo form 3 different layers of cells:
- first (outer) layer - ectoderm– will turn into the nervous system (including the brain, eyes, ears), skin and hair;
- second layer - endoderm– will become the liver, the lining of the intestinal tract, lungs, pancreas and thyroid glands;
- third layer - mesoderm– circulatory system, urogenital system, muscles, skeleton and heart.
By the end of the 4th week pregnancy, just 2 weeks from the beginning of the embryonic period, the heart of the fetus begins to beat and its nervous system begins to function, albeit in the most primitive form. The heart and nervous system contribute to the development of the embryo as a whole organism. All this happens with an embryo whose length is only 6 mm.
In a one-month-old embryo, you can find eyes that are located on the sides of the head; The facial structure of the fetus changes almost daily during the 2nd month.
During the 7-9th week From small rudiments of limbs on the body of the embryo, arms and legs are formed. The brain, digestive system, heart, kidneys and liver are already present.
By week 8 the rudiments of ears, eyes and even gums appear.
9-11 weeks: The baby already has a nose and fingers and toes. His head is still larger than his body. The eyes are already formed, although the child cannot see with them yet.
By the end of the first trimester of pregnancy, the baby's organs and features are formed. He begins to use his muscles.
At 10-11 weeks the child bends his fingers, and at 11-12 weeks can move them and clenches his fist. The baby is already approximately 5-6 cm in length and weighs approximately 14 g.
Blood circulates between the baby and the membrane with which it is attached to the wall of the uterus, and the placenta begins to function.
Thus, by the end of the first trimester of pregnancy, the child has not only a variety of sensory experiences, but also positive and negative emotional experiences that accompany a comfortable and uncomfortable state. The influence of the mother on the child during this period occurs through the functions of her body. The desire for pregnancy and a positive attitude towards the future appearance of a child in the first trimester of pregnancy help the mother to positively tolerate unpleasant changes in the woman’s condition during this period.
Fetal stage begins from the beginning of the third month of pregnancy and continues until the moment of birth, i.e. approximately 7 months out of a 9-month pregnancy period. It is at this time that most organs and systems of the body mature and begin to function. The fetus begins to move, “kick”, turn its head, and then its whole body. Despite his tightly closed eyelids, he tries to “direct his gaze”, moves his lips, opens his mouth, begins to gradually swallow amniotic fluid, practices breathing exercises in a liquid medium, makes sucking movements - and perhaps even sucks his thumb.
During the 3rd month further formation of somatic structures of the fetus is underway.
The eyes form the iris and all the nerves that connect the eye to the brain. Teeth form in the gums, and noticeable growth of the ears begins. The fetus develops the thyroid, thymus, pancreas and kidneys. The liver begins to function. The future baby has a functioning gastrointestinal system - the small intestine is already capable of contracting and pushing through water, from which it receives nutrients. The external genitalia are of sufficient size to confidently determine the sex of the child.
13-16 weeks: The baby receives all its nutrients from the placenta. It is 9 cm long. The baby's hair begins to grow. In the 4th month, the length of the body increases so that the head no longer looks disproportionately large as in previous months.
Lips become visible on the face, and the strength of the heart muscle increases so much that the heart rate begins to be 120-160 beats per minute.
17-20 weeks: From the 17th week, the baby begins to form a fat layer (or subcutaneous fat), which is involved in energy production and metabolism. Starting this week, the baby begins to react to loud noises, and he is unlikely to like loud noises. The baby's eyes are still closed, but he can now move them up and down. He develops eyebrows, fingernails and toenails. The child's body is covered with small vellus hair. At this point, the child’s movements become stronger and more noticeable.
At 20 weeks The organs of taste and smell develop. Body length is approximately 17 cm, weight – 280-300 g.
Thus, in the 5th month the fetus develops a grasping reflex, and the volume and strength of movements increases.
21-24 weeks: By 21 weeks, the baby’s digestive system is developed so that he can already swallow amniotic fluid. Together with it, the main amount of nutrients enters the child’s body. Scientists believe that ingesting amniotic fluid promotes the growth and development of the fetal digestive system. At week 24, the baby weighs approximately 570-580 g and is 21 cm long.
2 layers of skin are formed: epidermis and dermis. The epidermis is responsible for the formation of the skin pattern on the fingertips, palms, and feet, which is determined genetically. The dermis, located under the epidermis, forms outgrowths that contain nerve endings and blood vessels. During this period, the baby's skin is wrinkled, covered with vernix lubrication - a fatty substance that protects the skin from the effects of amniotic fluid.
By week 24 sweat glands begin to work, lungs form, but so far they cannot work independently. Skin sensitivity develops more fully and a reaction to sound appears. The eyes are fully formed and the eyelids can already open.
At the 6th month the child's head and torso become more and more proportional. The skeletal system is intensively developing, hair growth on the head continues, and the fetus begins to straighten. Also, the baby becomes more and more emotional and mobile. He can already get angry, worry, express his dissatisfaction - he knows how to tense the muscles around his eyes and wrinkle his lips, pretending to cry or smile.
An event that deserves special attention during the second trimester is brain development. The brain enlarges 6 times.
Thus, in the second trimester of pregnancy, the emotional state of the child - pleasure or displeasure - changes depending on the emotional state of the mother directly, through the mother’s hormones entering the blood. During this period, the child already reacts by changing motor activity in response to the emotional state of the mother. After 20 weeks of training, the child can respond with movements to certain tactile stimulation, and after 24-26 weeks - to tactile and auditory stimulation. The researcher believes that in this period we can talk about the fact of the child’s activity.
During the third trimester the maturation of diverse brain structures occurs, preparation for all body systems and the transformation of a fragile embryo into an infant actively adapting to its environment.
25-28 weeks: The facial features are already fully formed. The baby is good at distinguishing sounds and what is happening in the world around him. Distinguishes voices, noises, listens to music. Sounds that are too sharp frighten him. Approximate at 26 weeks The baby opens his eyes for the first time; they are already fully formed and can perceive light.
At 27 weeks the fetus sometimes turns its head towards the light directed at the mother's abdomen. In any case, brain scans confirm that he responds to light. In addition, the baby sees vague outlines of his arms and umbilical cord. At 28 weeks The child's tongue develops taste buds. The mass of the brain increases, and characteristic grooves and convolutions begin to appear on it. The child is actively recovering - this is due to an increase in the volume of subcutaneous tissue. The child already weighs about 1 kg.
At 7 months of age The fetal nervous system matures enough to control breathing and swallowing. The baby already feels touch and pain; perhaps his vestibular apparatus begins.
29-32 weeks: The child gains strength, accumulates fat, preparing for independent life. There is less and less space for him, so he is gradually determining his permanent position in his mother’s stomach.
The child's kidneys and bladder are actively working. During this period, the child coughs and hiccups. Almost all of the baby's wrinkles disappear. The hair on your head becomes thicker. Approximately at 30 weeks the child practices trying to focus his gaze. By the end of the 32nd week, the baby can weigh 1.7 kg and have a length including legs of 42 cm.
At the 8th month the fetus can gain weight up to 200 g per week. It is possible that from the 32nd week the baby begins to become aware of what is happening, because... many neural systems of the brain had already formed by this time. Brain scans show periods of rest that look like periods of paradoxical sleep.
33-36 weeks: As the fetus enters the 9th month of prenatal development, circadian sleep-wake cycles are established and hearing development is believed to be complete. The baby grew round, his skin became pink and smooth. The nails have grown and are beginning to protrude beyond the fingers.
By week 36 The child's face becomes plump and round cheeks appear. The child continues to suck his finger in the womb - he trains his sucking muscles. The baby's head may have already descended into the pelvic area, preparing for labor in advance.
The child gains 220 g every week. By the 36th week he already weighs 2.75 kg, and his height including legs reaches 46 cm.
37-40 weeks: The baby continues to gain weight in recent weeks. All organs and systems of the child have already developed and are in their places. The child has developed reflexes that help him perform grasping movements, blink, close his eyes, move his legs, raise and lower his head. At this time, vision and eye coordination improve, as well as the development of brain functions. The lungs and respiratory system develop last.
Now the child weighs from 3 to 3.4 kg and has grown to 48-50 cm.
Thus, over approximately a 9-month period, an initially single-celled zygote normally develops to 10 trillion cells, organized into organs and systems.
Thus, in the third trimester, the child develops preferences for various types of sound stimulation: the mother’s voice, her heartbeat, musical and speech phrases, songs, melodies, poems, and selectivity for the cultural characteristics of food develops. Positive maternal emotions have a beneficial effect on the development of not only sensory perception, but also the prerequisites for intrauterine self-awareness.
By the 6th month of pregnancy (by the 25th week), the child is able to translate sensations into emotions; the baby’s internal reality begins to take shape under the influence of emotional information from the mother.
The prenatal period of a child’s development is a wonderful time when parents, and especially the mother, can fully influence the processes of formation of not only the physiology of their child, but also his mental, intellectual and spiritual health.
