What is mrm on ultrasound during pregnancy. What is fetometry and why do you need to know the parameters of the fetus during pregnancy? Normal values, mm
When a new life grows inside a woman, she is ready to rebuild and change her whole habitual life and way of life, to give up many favorite habits, if only the long-awaited beloved baby is born healthy.
However, unfortunately, not everything depends only on the desire of the mother, because the body of the crumbs is so fragile.
Therefore, during pregnancy and when planning it, you need to be careful, take care of your health, and of course, follow all the advice and recommendations of your doctor.
A pregnant woman undergoes a lot of examinations during the period of bearing a child, but one of the most effective, harmless and reliable diagnostic procedures is ultrasound.
With the help of this study, doctors can assess the state of health of the woman herself, the well-being and health of the baby, see how it develops, etc. As part of the ultrasound, as a rule, fetometry is also always performed.
Do not be afraid of the unusual name of the study: it does not mean anything terrible, rather, on the contrary, because “fetus” is translated from Latin as “fruit”.
So, doctors call fetometry measurements of a child in utero, in order to determine how the development of his body proceeds, to identify possible visible disorders or to diagnose other problems.
Measurements are usually taken in millimeters, while doctors follow the proposed tables, which indicate what exactly needs to be measured.
Then the result will be compared with the existing standard - for each week, its own parameters are adopted in order to assess how symmetrically the baby develops, and whether this development corresponds to the declared gestational age.
When and how does the study take place?
Fetometry is carried out as planned three times, as well as ultrasound diagnostics:
- in the first trimester (at 11-12 weeks);
- in the second (at 20-22 weeks);
- in the third (mostly at 32 weeks).
In the first trimester, as part of a fetometric study, the diagnostician will confirm the date of birth suggested by your gynecologist. The main task of the doctor at this stage is the exclusion of chromosomal abnormalities and gross malformations. The most important indicators now will be the coccyx-parietal size (KTR) and abdominal circumference.
Also, during the screening ultrasound, both the thickness of the collar space and the length of the nasal bone are measured.
Ultrasound examination in the second trimester is performed to check the absence of intrauterine developmental disorders. For this, the main measurements are taken: biparietal size of the fetal head, CTE, head circumference, tummy circumference, fronto-occipital size.
Perhaps other indicators will be taken: the length of the baby's thigh and the length of other bones (tibia, shoulder, elbow). At this visit to the doctor, you have a chance to find out the gender of your unborn child.
Diagnosis in the third trimester no longer sets itself the task of finding some kind of defects or disorders, because before that time the baby is already fully formed and is preparing for the birth.
Now it is important for the doctor to check his well-being and state of health. He will also measure the circumference of the head and tummy, see how symmetrically the child's limbs develop, determine his weight and height.
These indicators will be important for choosing a method of delivery (too large fetal sizes, first pregnancy, narrow pelvis and other features can cause a referral to a caesarean section). If everything is in order, no more procedure is prescribed.
Since we are talking about a diagnostic component of ultrasound, it goes without saying that fetometry can be performed, like the ultrasound itself - transvaginally or transabdominally.
The first method is often used in the early stages or to clarify the information of interest to the doctor (then the sensor device, previously dressed in a condom, is inserted into the woman's vagina).
If the pregnant woman does not suffer from excess weight, and the anterior abdominal wall does not prevent the doctor from seeing important parameters of the baby’s development, then even the first planned ultrasound is done transabdominally (the stomach is lubricated with a special gel and a sensor is driven over it).
The procedure does not require special preparation. In the first trimester, for a routine study, you will need to drink 1-1.5 liters of water an hour before the procedure, and then, as the baby grows in the uterus, this need will disappear.
The main nuances of the examination of the fetus
Since the development of the baby occurs, as if, in jumps, or in waves, the results of all fetometric indicators should be thoroughly studied and deciphered by the doctor observing your pregnancy.
Even a highly qualified specialist will not draw independent conclusions based only on fetometry data.
Each person (and the tiny baby in the mother's belly) is individual in his development, and the physiological characteristics of his body are also individual. For example, the father and mother of a child are tall and have a large build.
Of course, the fetometric indicators will exceed all the average parameters that should correspond to a certain gestational age. The same is with low weight, and with other individual characteristics that depend on hereditary factors.
There are several forms of developmental delay:
- a symmetrical form is fixed when all indicators of the fetometric study are lower than the normal values \u200b\u200bfor this gestational age;
- with an asymmetric form, the diagnostician will observe the norm in relation to one parameter, and the predominant decrease in some other indicators.
Three degrees are also distinguished for determining the lag in fetometry parameters:
- the first degree means a difference with the norm of two weeks;
- the second - in 3-4;
- the third - more than a month.
Sometimes the doctor repeats the procedure after some time, and the parameters return to normal, so you should not just be scared if the numbers of your study differ from the book indicators.
In the case of a large difference, additional diagnostic methods will be prescribed to exclude all kinds of pathologies and malformations, developmental disorders, stopping or delaying vital activity.
Key points of the fetometric study
As already mentioned, tracking of various parameters of the child occurs gradually, depending on the gestational age. The fact is that in the early stages of development, the fetus is still so small that even high-precision devices and modern equipment cannot determine much.
In addition, all the organs and systems of the crumbs have just begun their formation, laying and development, so the diagnosis at the beginning of pregnancy will simply be inconclusive. When the time comes for scheduled examinations, the doctor will be able to see and record all the necessary indicators.
Baby weight
One of the most important and indicative parameters monitored throughout pregnancy is the weight of the fetus by week.
If the problem was noticed in a timely manner, then by taking preventive measures, it will be relatively easy to correct the situation.
Depending on the period, the baby can gain from ten to one hundred grams in a week. At the first examination, he will be very small, but before the second and, especially, the third diagnosis, he will noticeably gain weight.
Of course, the rate of weight gain, as well as growth rates or other features, is different for each child. The genetic factor is of great importance in this matter.
The main thing that doctors pay attention to is the positive dynamics of weight gain.
KTR or coccyx-parietal size - is considered the best parameter for determining the term at the very beginning of pregnancy. It is used to evaluate the child, no larger than 20-60 mm in size. As part of the study, the diagnostician measures the distance from the crown (head) to the coccyx.
KTR norms are included in the protocol of the first ultrasound screening.
Starting from the second trimester, special attention is paid to the biparietal size of the baby's head. Focusing on its indicators, doctors can determine how the baby's brain develops. The measurement is made along the axis of the head (by the distance from one temple to another).
Based on the data of the indicator of the biparietal head size, it is possible to determine the gestational age with an accuracy of seven to eleven days.
The shape of the head is also evaluated, its circumference, fronto-occipital size are measured.
Determination of thigh length
The length of the femur is also an important indicator of development.
Specialists estimate the gestational age, based on its results, only in cases where the shape of the head has changed significantly, or the BDP indicator could not be derived.
Accuracy, however, can fluctuate up to two or more weeks.
As for the measurement of other bones, the estimation of the gestational age based on their result is even less accurate.
Abdominal circumference
The circumference of the tummy is the characteristic that helps to explore the intrauterine development of the child in more detail. This parameter is very important, because with its help the doctor studies whether the baby’s organs are developing correctly: they visualize the stomach, gallbladder, a short segment of the umbilical vein and the venous duct.
Indicators of tummy circumference are less accurate than indicators of BDP or DB, for example, but still doctors consider this parameter to be the most informative when assessing growth, etc. Also, OB is taken as a criterion for intrauterine growth retardation.
This measurement is not carried out if the child weighs more than 4 kg.
chest volume
An indicator that can give maximum information for a period of 14-22 weeks. However, doctors always prefer to use several parameters: firstly, it helps to improve the accuracy of the term estimate, and secondly, it will allow you to notice any problems or complications in time.
In addition to these key parameters, the development and growth of other organs and systems are assessed, as well as the woman's health status, the general course of pregnancy and other factors.
For all women, pregnancy is a special life stage. At this time, the expectant mother experiences new sensations and, on the other hand, learns her essence. Along with positive emotions and fantasies about the future baby, a young mother has to undergo many consultations and take many tests. Such visits to the clinic sometimes make you nervous. But tests are necessary to control the normal growth and development of the baby in the woman's tummy.
When is an ultrasound needed?
When the expectant mother comes to see her doctor, she is explained the need and timing of the observations under the ultrasound machine. There are two types of ultrasound: screenings and selective studies. Screening is the mandatory examination of all pregnant women with the help of ultrasound at a certain time. Usually, a planned ultrasound examination of the expectant mother takes place at terms from 10 to 12 weeks, from 22 to 24 weeks, at 32 and 37-38 obstetric weeks of pregnancy. When conducting this type of examination, the size of the fetus and their compliance with the norms, the duration of pregnancy, the condition of the uterus and placenta are measured. Selective studies are prescribed by the attending physician if there is a suspicion of a pregnancy complication. In the case of determining the pathology of pregnancy, such examinations can be carried out an unlimited number of times.
Fetometry - what is it and why
One of the important procedures is fetometry of the fetus. During the procedure, the doctor analyzes the size of the fetus and its compliance with the norm. The procedure is an ultrasound examination, the data of which the specialist compares with the tables of norms. The test helps to detect defects and deviations in the development of the baby in time. When carrying out fetometry, the circumference of the fetal head is determined by weeks - the norm is an important indicator. For weeks, the doctor fixes the ultrasound values and draws conclusions about the health of the baby. When the doctor states that the size of the fetus is smaller than that established for a given period, then they speak of a slowdown in fetal growth. If, over the course of the pregnancy, a lag of a couple of weeks appears, then doctors talk about intrauterine growth retardation. Such a delay can be caused by bad habits of the mother, internal infections, chromosomal abnormalities, or placental insufficiency.
Table of contents [Show]
Table of indicators of fetometry of the fetus - these are the norms of various sizes of an intrauterine developing child, determined by ultrasound. It was compiled on the basis of measurements carried out in a large sample and subsequent statistical analysis of the results. It is this table that is the basis for determining the gestational age.
In addition, by comparing the sizes obtained for a particular child with the norms, the symmetry of its development and compliance with the calculated gestational age are assessed.
How to prepare for the study
The measurement of an intrauterine developing baby is carried out during an ultrasound scan. This study can be performed both with a transvaginal sensor and through the anterior wall of the abdomen.
If the procedure will be carried out through the vagina, preparation for fetometry of the fetus is not necessary. If a transabdominal ultrasound is planned, then in the early stages of pregnancy you will need to before the examination, drink about half a liter of water an hour before the examination and do not go to the toilet after that.
This is necessary so that through a full bladder, as through a window, you can look into the uterine cavity. In terms of more than 12 weeks, this is no longer required, since the necessary “window” is created by amniotic fluid.
How is the procedure for measuring the parameters of the baby
A woman comes to the ultrasound room, where she undergoes a regular ultrasound examination - through the wall of the abdomen (then the stomach is lubricated with a special gel) or through the vagina (a condom is put on the sensor).
Which table will help you find out what period your baby corresponds to
The fetal fetometry data table consists of quite a few indicators. From 5 to 13 weeks, only three sizes of the fetus are evaluated by ultrasound:
- coccygeal-parietal size (CRL, KTR) is the maximum distance that can be measured from the head to the tailbone
- biparietal distance (BPD, BDP) can be measured from one to the other parietal bone, that is, we can say that this is the diameter of the head
- fetal egg (PY) is the volume of the cavity in which the baby develops; later, both the placenta and the waters around it will appear there.
| Term | ПЯ, mm | BPD, mm | CRL, mm |
| 5 | 5 | 1-3 | |
| 6 | 13 | 4-6 | |
| 7 | 21 | 3 | 8-10 |
| 8 | 29 | 7 | 14-16 |
| 9 | 36 | 10 | 22-23 |
| 10 | 44 | 14 | 31-32 |
| 11 | 51 | 17 | 41-43 |
| 12 | 57 | 20-22 | 42-73 |
| 13 | 63 | 24-26 | 51-87 |
This is how the ultrasound table of fetal sizes looks like, with which they are compared for compliance with the norm.
What parameters are evaluated from 13 weeks
The size of the child on ultrasound is estimated based on:
- OG - circumference (girth) of the head
- BDP - biparietal size (BPD), that is, the distance between the most distant points of the parietal bones from each other
- DB - femur in length
- LZR - fronto-occipital size, that is, the distance between the most distant points of the forehead and the back of the head
- OC - circumference (girth) of the abdomen
- SDJ - diameter of the abdomen in the anterior-posterior direction, that is, the sagittal size
- PJ is the diameter of the abdomen in diameter
- OG (or DRGK) - circumference (girth) of the chest
- DP - length of the humerus
- There are also lengths for the tibia, fibula, radius and ulna, and foot. Each of them has its own norm.
You can evaluate pregnancy by fetometry by comparing the indicators indicated in the transcript of your ultrasound personally with the standard parameters in the available tables.
It is especially important to compare the BDP or the coccygeal-parietal distance - it is these 2 criteria that are fundamental for determining the gestational age by ultrasound.
| Term in weeks | LZD | BPD | OG | coolant | SJ | PJ | DB | DP | Dl.M.Bertz | Dl.B.berts | DgrK |
| 13 | 32 | 96 | 67 | 21 | 22 | 11 | 10 | 8 | 9 | 24 | |
| 14 | 35 | 26 | 106 | 78 | 24 | 25 | 15 | 13 | 11 | 12 | 26 |
| 15 | 39 | 32 | 118 | 89 | 28 | 29 | 18 | 17 | 14 | 15 | 28 |
| 16 | 43 | 35 | 130 | 100 | 31 | 32 | 21 | 20 | 17 | 18 | 34 |
| 17 | 47 | 39 | 143 | 111 | 35 | 36 | 24 | 23 | 20 | 21 | 38 |
| 18 | 52 | 42 | 155 | 122 | 38 | 39 | 27 | 26 | 2 | 24 | 41 |
| 19 | 56 | 44 | 168 | 132 | 42 | 43 | 30 | 28 | 25 | 26 | 44 |
Fetometry of the fetus at 20 weeks presents such indicators (data - in mm)
- BPR: 47-49
- OG:181
- DGRK: 48
- LZR: 60
- coolant: 143
- PJ: 46
- SJ: 45
- thigh length: 33
- normal length of the tibia: 29
- fibula length: 28
- shoulder length: 31
- length of forearm bones (radius/ulna) = 25/28
- the foot of a 20-week-old fetus is 33.
Fetometry of the fetus at 22 weeks is represented by such indicators in millimeters
- BPR: 54-56
- OG: 206
- DGRK: 53
- coolant: 165
- PJ: 53
- SJ: 52
- thigh: 39
- fibula/tibia (lower leg): 33/34
- shoulder: 36
- radius/ulna = 30/33
Fetometric parameters at 23 weeks (indicators in millimeters)
In the photo: an embryo on ultrasound at 6-7 weeks of pregnancy
- BPR: 57-59
- OG: 218
- DGRK: 56
- coolant: 175
- PJ: 55
- SJ: 56
- hip: 41
- drumstick = 35/36
- shoulder: 38
- forearm: 32/35
- height: 31 cm
- 580-600
Fetometry of the fetus after reaching 31 weeks (numbers are in mm)
- BPR: 80-82
- OG: 301
- DGRK: 81
- coolant: 258
- PJ: 82
- SJ: 81
- thigh: 60
- lower leg = 51/52 mm
- shoulder: 54
- forearm bones = 44/50
- height: 42 cm
- body weight: 1590-1690.
The norms of fetometry at 32 weeks on average look like this (mm)
- BPR: 83-85
- OG: 309
- DGRK: 83
- coolant: 266
- PJ: 85
- SJ: 84
- thigh: 62
- lower leg = 52/54
- shoulder: 55
- forearm bones = 46/52 mm
- height: 43
- weight: 1790-1890.
Fetometry of the fetus at 33 weeks can be presented in the form of such a table
Fetometric data at 34 weeks in millimeters
- maximum distance between the parietal bones (BDP): 89
- head girth (OG): 323
- chest across (DHRC): 88
- abdominal circumference (OJ): 285
- PJ: 91
- SJ: 90
- thigh: 66
- lower leg = 56/57 mm
- shoulder: 59
- forearm bones = 48/55
- height: 46-47 cm
- body weight: 2270-2390.
Fetometry at 36 weeks (mm)
- BDP: 92
- OG: 335
- DGRK: 94
- coolant: 303
- PJ: 97
- SJ: 96
- thigh: 70
- lower leg bones: 58/60
- shoulder: 61
- forearm bones = 50/57
- height: 49 cm
- body weight: 2750-2860.
Fetometry at 37 weeks
- BDP: 94
- OG: 339
- DGRK: 97
- coolant: 311
- PJ: 100
- SJ: 98
- thigh: 71
- drumstick: 60/62
- shoulder: 63
- forearm bones = 51/58
- height: 50 cm
- weight: 2970-3090.
The main parameters that are important for the correct assessment of the baby in the first two trimesters are the abdominal circumference, biparietal size and thigh length.
After this period, just before childbirth, the circumference of the chest, the circumference of the abdomen and the length of the femur become more important.
What is "norm"
It is considered normal if your child's data correspond to the size of the fetus by week of ultrasound, and if they lag behind or exceed the period calculated by your gynecologist, then by less than 14 days.
The norm is also if the indicators are not located on the same line, but have a small spread, which occurs because the child grows in leaps and bounds.
If, for example, everything “fits” into the norm, except for the length of the thigh and tibia, this does not yet indicate pathology. Maybe the child's parents or older relatives do not have a long leg.
A situation is considered dangerous when, according to fetometry, it is not the first time that it is noticeable that one of the circles is more or less than 2 lines in comparison with the rest of the indicators. This should be seen as a health hazard.
For example, if the head circumference grows, this may indicate intrauterine hydrocephalus; if it is less and less consistent with the deadline, this may indicate a different pathology of the brain. In this case, the measurement of the size of the baby by ultrasound is supplemented by dopplerometry, CTG and obligatory observation in dynamics.
However, the diagnosis of "Intrauterine growth retardation" or "Hypotrophy" is within the competence of a joint assessment of the parameters of ultrasonic fetometry by two doctors: an obstetrician-gynecologist and a medical geneticist.
Only these specialists can assess your genetic predisposition, and, in case of a disappointing diagnosis, they will be able to find the causes of such a pathology. So, these are chromosomal abnormalities, and bad habits, and the age of one or two parents, and an infection that has got to the intrauterine developing child.
Given all of the above, it is necessary that the obstetrician-gynecologist deal with the decoding of the indicators of this study: the ultrasound doctor only provides him with data in which he indicates what and how much it differs from the norm.
The price of such a study is included in the cost of ultrasound during pregnancy and ranges from 500 to 1200 rubles.
Thus, what the table of indicators of fetal fetometry represents is averaged data. They are guided in order to determine whether the gestational age calculated by the obstetrician corresponds to that obtained from these data. According to the same parameters, they look at whether the growth of the baby is symmetrical (when everything is lower or higher by 1-2 lines), or, conversely, asymmetrically. This allows time to identify some malformations.
ATTENTION! The information on the site is for reference or popular, is for informational purposes only. Proper treatment and prescribing of drugs can only be carried out by a qualified specialist, taking into account the diagnosis and medical history.
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- The essence of the procedure
- Norms and deviations
- Description of key indicators
- I trimester
- II trimester
- III trimester
At various stages of pregnancy, fetometry is regularly performed - this is the determination of the size of the fetus through ultrasound. The data obtained during the survey were subjected to statistical analysis over the years, and on their basis a table was compiled with weekly norm indicators.
It is the main parameter for a more accurate determination of the period and allows you to find out if there are any deviations in the intrauterine development of the baby. Knowing what it is, young parents themselves can, after an ultrasound examination, make sure that everything is in order.
The essence of the procedure
Most often, ultrasound fetometry is performed either with a transvaginal sensor, or traditionally through the abdomen. In the first case, no preparation is required from the woman. A classic ultrasound will show more accurate results if you drink 500 ml of water an hour before the procedure and do not empty your bladder in the early stages. Filled, it will help improve visibility in the uterine cavity. After 12 weeks, this is no longer required, since this function will be performed by amniotic fluid.
The procedure is familiar to everyone: a special gel is applied to the stomach, and everything that happens in utero is displayed on a computer monitor. Modern programs allow you to automatically take measurements of the fetus, and the doctor then compares them with the general table of norms for weeks. This allows you to clarify the gestational age and timely identify pathologies in the development of the fetus.
Why is it called so? The term "fetometry" goes back to the Latin word "fetus" (translated as "offspring") and the Greek "metreo" (meaning "to measure, determine").
Norms and deviations
It is useful for parents to know what the norm is, according to the fetometry table, and when they talk about pathological abnormalities. Seeing a slight discrepancy between the true sizes and official figures, many begin to panic and draw the wrong conclusions, which in most cases turns out to be completely in vain.
- the data of the fetus fully correspond to the sizes in the table;
- they are less than 2 weeks behind or ahead of them (this period is acceptable for individual characteristics);
- the indicators are not on the same line, but scattered, but this difference is no more than 1 line: these discrepancies are acceptable due to the spasmodic intrauterine development of the fetus.
Everything else is considered a deviation. It is especially dangerous when the fetometry of the fetus once again shows that the same size is more or less than the norm by 2 or even more lines.
For example, a growing head circumference may indicate hydrocephalus, but additional data obtained during dopplerometry and CTG, and follow-up will be needed to confirm the diagnosis.
For comparison. If all dimensions of the fetus "fit" into the norm indicated in the fetometry table, except, for example, the length of the thigh, this is not at all an indicator of pathology. Perhaps the parents or other relatives of the child are simply the owners of very long (or, conversely, too short) legs.
In the presence of deviations, such serious diagnoses as "intrauterine growth retardation", "hypotrophy" are confirmed by two doctors: not only an obstetrician-gynecologist, but also a medical geneticist. They assess the genetic predisposition of the fetus and determine the causes of the identified pathology (chromosomal abnormalities, bad habits, parental age, intrauterine infection, etc.).
It is very important that the obstetrician-gynecologist is primarily involved in deciphering the obtained indicators: the ultrasound specialist only provides him with a summary sheet, which indicates what sizes and how much they differ from the norm of fetometry for a given gestational age. What parameters are taken into account during screenings?
Description of key indicators
To figure out what weekly fetal fetometry data are contained in the tables, you need to know the symbols for these parameters and their interpretation.
- BDP - biparietal size, the distance between the parietal bones, describes the development of the nervous system.
- DB - thigh length.
- DG - leg length.
- DN - the length of the nasal bone.
- DP - shoulder length.
- KTR - coccyx-parietal size.
- LZR - fronto-occipital size.
- OG - head circumference.
- OG (DHA) - chest volume (diameter of the chest).
- OC - abdominal circumference.
- PJ - transverse diameter of the abdomen.
- PYa - a fetal egg where the child develops.
- SJ - sagittal diameter of the abdomen (measured in the anterior-posterior direction).
- TVP - the thickness of the collar space.
This is the interpretation of the indicators that are most often indicated in the fetometry table. It may also include the lengths of other bones - more - and fibula, ulna, radius, as well as the foot. But they no longer have such significance for the detection of pathologies - they are used for comparison only as additional information.
Among other things, you can calculate the weight of the fetus by fetometry, carried out after the 20th week of pregnancy. All calculations are made automatically by the ultrasound machine itself based on the term, BPR, LZR, OZH, DB and OG. They give very accurate results and allow you to compare them according to the table with the norms.
I trimester
The first fetometry is prescribed at 12-13 weeks. Its purpose is to identify fetal malformations in early pregnancy.
This ultrasound screening does not identify a specific disease, but only points to markers that are typical for it. Based on the results obtained, additional studies may be prescribed. All suspicions that have arisen are confirmed or refuted by invasive laboratory techniques.
Some indicators of fetometry can be specified. For example, during the first screening, specialists use a table of average CTE values, since this size is very important for identifying abnormalities in the intrauterine development of the fetus.
Doctors include an increase in CTE by 1-2 weeks to the variants of the norm. If the pregnancy is not complicated by the mother's diabetes mellitus and Rhesus conflict, this may mean that the baby will be born a real hero and its weight will be more than 4 kg, and in some cases this may be an indication for a caesarean section.
These are the important data that the first fetometry gives into the hands of specialists.
About the timing. The first ultrasound screening is carried out during this period because of the TBP indicator. Until 11 weeks, it is so small that it cannot be measured. And after 14 weeks, this space is filled with lymph, which distorts the results of the study. It is this parameter that is a marker for most fetal chromosomal abnormalities.
II trimester
The time frame for the second ultrasound fetometry should be within the following timeframes:
- not earlier than 16 weeks;
- no later than 20;
- the best option is week 17, which, if abnormalities are detected, will allow more accurate additional genetic examinations;
- sometimes ultrasound is also performed at 21-22 weeks, but these are already the most extreme and undesirable dates.
The first ultrasound screening gives the most accurate results, but often even they are not enough to make a diagnosis. To do this, many indicators need to be seen in dynamics. Here it is just the data of the second fetometry that demonstrate it.
It performs the following tasks:
- identify defects that cannot be determined in the first trimester;
- confirm / refute the diagnosis previously made based on the results of the first screening;
- determine the level of risk of suspected fetal pathologies;
- detect deviations in the formation of a small organism.
Fetometry II trimester is assigned only to those women who, according to the results of the first ultrasound, were at risk.
Approximate norms of ultrasound at this stage of pregnancy are presented in the following tables.
Height Weight
Abdominal circumference
Head circumference
Calf length
Thigh length
Humerus length
Forearm bone length
If for some reason the timing of the second fetometry was shifted, you can use a table with averages from 21 to 27 weeks:
After examining the data of the second fetometry, the gynecologist can refer the woman for a consultation with a geneticist or independently prescribe invasive techniques to diagnose suspected pathologies. In cases where the diagnosis is still confirmed, a decision is made about the future of the pregnancy.
If therapeutic adjustment is not possible, artificial induction of labor is performed (read about artificial labor in our article). If the detected pathology is reversible, treatment is prescribed as soon as possible in order to save the baby.
III trimester
The third fetometry can be prescribed on any day of the III trimester of pregnancy. The optimal period is 32-33 weeks. Since at this stage the matter is approaching childbirth, ultrasound is carried out more carefully than before.
For example, the baby's face is already perfectly visible, which makes it possible to identify such pathologies as the cleft palate or cleft lip. The doctor finds out how developed the fetus is in accordance with the gestational age.
It is usually not recommended to conduct such studies after 34 weeks. However, there are cases when they are appointed immediately before the birth itself (at 37-38 weeks) in order to make the final decision on a caesarean section or a natural birth of a baby.
Table of average values of the third fetometry of the fetus by week
If there are deviations at this stage, the woman is offered hospitalization. With the negative dynamics of the testimony received, doctors may decide to stimulate preterm labor.
Helpful information. Everyone around (women, and often doctors themselves) like to talk about the importance of the first two fetometry and the optionality of the third. But after all, only she allows you to make the right decision on how to carry out the upcoming birth with minimal losses for mom and baby.
Information from the tables of fetometry of the fetus is for informational purposes only. It is not recommended for parents to draw any independent conclusions by comparing the results obtained with the norms, because they do not always reflect reality and require mandatory interpretation by specialists.
Expectant mothers in the process of bearing a baby have to undergo a large number of examinations, including fetometry using ultrasound. This is one of the few non-traumatic procedures that can provide reliable information about the condition and development of the child throughout pregnancy.
Fetometry of the fetus, as a method, is the determination of the size of the baby by means of ultrasound scanning and the comparison of the data obtained with the existing standards. This information allows the attending physician to judge the occurrence of developmental anomalies or the normal process of gestation.
If there are difficulties with establishing the term of conception for the last menstruation, fetometry of the fetus allows you to determine it with an accuracy of 4 days. Therefore, we can say that this method is in demand in the early diagnosis of intrauterine development disorders and specifying the timing of pregnancy. All norms of fetal fetometry indicators are brought to the world standards of medicine and are indicated in tables with average statistical data.
Periods of passing a fetometric study
Ultrasound examinations to diagnose the development of the baby are usually timed to coincide with the 12th, 20th and 32nd weeks of pregnancy. There is one diagnostic procedure for each trimester.
The decision about the time of ultrasound and fetometry is made by the doctor. This is affected by:
- general condition of the expectant mother;
- the emergence of suspicions of a violation of the intrauterine development of the child;
- established dates for fetometry of the fetus.
Thanks to ultrasound, it became possible not only to evaluate the main characteristics of the fetus (calculate the weight of the fetus by ultrasound, its height, chest and head circumference) and correlate them with the average indicators for weeks of pregnancy, but also to identify the functional state of the internal organs of the child, to determine its gender.
Thanks to modern ultrasound diagnostics, the doctor can not only compare fetometric data with the norm, but also evaluate the development of internal organs and determine the sex of the child.Key characteristics of fetometric research
The leading criteria for fetometry of the fetus are:
- KTP (coccyx-parietal size);
- BDP (biparietal head size);
- OG (chest circumference);
- coolant (abdominal circumference);
- DB (length of the thigh bone).
Table with average fetometry values by week of pregnancy:
| 13 | 24 | — | 69 | 9 | 31 | 10 |
| 14 | 27 | — | 78 | 13 | 52 | 12,3 |
| 15 | 31 | 39 | 90 | 17 | 77 | 14,2 |
| 16 | 34 | 45 | 102 | 21 | 118 | 16,4 |
| 17 | 38 | 50 | 112 | 25 | 160 | 18 |
| 18 | 43 | 53 | 124 | 30 | 217 | 20,3 |
| 19 | 47 | 57 | 134 | 33 | 270 | 22,1 |
| 20 | 50 | 62 | 144 | 35 | 345 | 24,1 |
| 21 | 53 | 65 | 157 | 37 | 416 | 25,9 |
| 22 | 57 | 69 | 169 | 40 | 506 | 27,8 |
| 23 | 60 | 72 | 181 | 42 | 607 | 29,7 |
| 24 | 63 | 76 | 193 | 45 | 733 | 31,2 |
| 25 | 66 | 79 | 206 | 48 | 844 | 32,4 |
| 26 | 69 | 83 | 217 | 49 | 969 | 33,9 |
| 27 | 73 | 87 | 229 | 52 | 1135 | 35,5 |
| 28 | 76 | 89 | 241 | 55 | 1319 | 37,2 |
| 29 | 78 | 92 | 253 | 58 | 1482 | 38,6 |
| 30 | 81 | 95 | 264 | 60 | 1636 | 39,9 |
| 31 | 83 | 97 | 274 | 62 | 1779 | 41,1 |
| 32 | 85 | 100 | 286 | 63 | 1930 | 42,3 |
| 33 | 86 | 102 | 296 | 65 | 2088 | 43,6 |
| 34 | 88 | 104 | 306 | 67 | 2248 | 44,5 |
| 35 | 89 | 106 | 315 | 69 | 2414 | 45,4 |
| 36 | 91 | 108 | 323 | 71 | 2612 | 46,6 |
| 37 | 93 | 109 | 330 | 73 | 2820 | 47,9 |
| 38 | 94 | 110 | 336 | 74 | 2992 | 49 |
| 39 | 95 | 112 | 342 | 75 | 3170 | 50,2 |
| 40 | 96 | 116 | 347 | 76 | 3373 | 51,3 |
Additionally, the following ultrasound indicators can also be determined:
- fetal head circumference;
- fronto-occipital size;
- leg bone length;
- tibia length;
- foot length;
- the length of the bones of the shoulder and forearm;
- norms of the bones of the nose;
- interhemispheric size of the cerebellum (MRM);
- heart diameter.
Indicators of the development of the back of the nose are very important for assessing the development of the child in the framework of identifying chromosomal diseases and birth defects KTR as a characteristic of the physical development of the fetus
KTR on ultrasound is an indicator recorded during fetometry, which reflects the size of the child (from the coccyx to the crown of the head) and is used as a determinant of the date of conception of the baby and the period of its gestation. There is a special table that shows the average-normal indicators, as well as the limits of permissible fluctuations of this value. Within these fluctuations, nothing threatens the healthy development of the baby.
Quite often, the KTR indicators obtained using ultrasound do not correspond to the average value, this is especially noticeable in the II trimester. The gestational age, determined by ultrasound, has a normal error of up to 4 days in both directions. KTR is measured up to 16 weeks, in the later stages other indicators are significant.
Table of average CTE values (according to the timing of the first screening ultrasound):
| Deadline, weeks + day | 10 weeks | + 1 day | + 2 days | + 3 days | + 4 days | + 5 days | + 6 days |
| KTR, mm | 31 | 33 | 34 | 35 | 37 | 39 | 41 |
| Deadline, weeks + day | 11 weeks | + 1 day | + 2 days | + 3 days | + 4 days | + 5 days | + 6 days |
| KTR, mm | 42 | 43 | 44 | 45 | 47 | 48 | 49 |
| Deadline, weeks + day | 12 weeks | + 1 day | + 2 days | + 3 days | + 4 days | + 5 days | + 6 days |
| KTR, mm | 51 | 53 | 55 | 57 | 59 | 61 | 62 |
| Deadline, weeks + day | 13 weeks | + 1 day | + 2 days | + 3 days | + 4 days | + 5 days | + 6 days |
| KTR, mm | 63 | 65 | 66 | 68 | 70 | 72 | 74 |
Variants of the norm include an increase in CTE by one to two weeks. If the Rh conflict, neoplasms and diabetes of the mother are excluded, then such an increase in the size of the baby may indicate that the child will be born large, with a weight of 4 kg or more.
In this case, it is necessary to use with caution medications that affect metabolism, including complex vitamins. Such drugs can lead to the birth of a very large child from 5 kg.
The reasons that can lead to a decrease in CTE can be both normal variants and a sign of severe pathology.
To the norm options includes the possibility of later fertilization due to the timing of ovulation. As you can see, the time of conception will be somewhat later than calculated in accordance with the last day of menstruation. In this situation, you just need to repeat the ultrasound in a week.
Causes of a pathological nature:
- Frozen pregnancy and death of the embryo. This situation requires immediate intervention and medical assistance, because. can cause bleeding, impaired reproductive functions of the female body, toxic shock and death of the mother. This pathology can be excluded if the heartbeat of the unborn child is determined.
- Lack of hormones (often progesterone) - requires confirmation with the help of additional research methods and hormone therapy (only a doctor can prescribe it!). Treatment is mandatory, because. hormonal deficiency can cause self-abortion.
- Infections, including STIs, can be a factor that negatively affects the growth of the baby. In this situation, additional examinations are needed to identify the infectious agent. Then therapy should be carried out within the permitted time frame.
- Genetic anomalies (syndromes: Down, Patau, Edwards). If such disorders are suspected, a genetic consultation and additional examinations are required. Serious genetic abnormalities usually lead to self-abortion.
- Somatic diseases of the mother, including chronic diseases of the heart and thyroid gland. As a rule, they exert their influence at a later date. And yet it is impossible to exclude their influence from the first week of development of the embryo.
- Pathology of the mucosa lining the uterus. Erosions, abortions, fibroids, violating the integrity of the mucous layer, prevent the fetal egg from properly gaining a foothold in the uterine wall and growing fully, which can cause self-abortion.
Insufficient KTR indicators, according to the table of standards, may indicate violations of the intrauterine development of the child, therefore, such a pregnancy needs additional examination
KTP is an important indicator of the development of the crumbs, but do not rush to interpret its value yourself, wait for the comments of the attending physician.
BDP as an indicator of the development of the fetal nervous system
The biparietal indicator, measured during fetometry, indirectly describes the development of the baby's nervous system and indicates the gestational age with a high degree of accuracy. In fact, BDP on ultrasound is the distance between the external visible boundaries of oppositely located parietal bones of the skull (right and left), which is determined along the line of the eyebrows. Often this parameter is measured together with the LZR indicator (frontal-occipital size) - the distance between the outer visible boundaries of the bones: occipital and frontal.
The characteristics of the BDP are used to determine the degree of safety for the mother and child of passing it through the birth canal during delivery. In the case when the value of BDP significantly exceeds the norm, operative delivery by caesarean section is indicated.
The BPR indicator in combination with the LZR indicator allows you to weekly evaluate the characteristics of the brain and the development of the baby's nervous system. A feature of biparietal characteristics is the slowdown in their growth with increasing gestational age.
At twelve weeks, the increase in BDP is about 4 mm per week, by the end of the gestation period, it barely reaches 1.3 mm. A competent interpretation of this indicator makes it possible with a high level of reliability to assess the growth and development of the baby throughout the entire period of gestation.
Slight fluctuations in the biparietal and fronto-occipital indicators may be options for the normal growth of the baby. For example, if the fetus is large (over 4 kg), then all parameters can be increased for a period of one to several weeks. Also, sometimes the head grows a little more / less than other organs, because the baby grows unevenly. In this situation, you need to repeat the ultrasound in a few weeks, perhaps the indicators will even out.
If the doctor diagnosed the patient with a large-fetal pregnancy, then the indicators of BPR and LZR can be naturally increased in accordance with the size and weight of the baby
A significant increase in these indicators can be an alarming symptom, indicating the development of neoplasms of bone or brain structures, the appearance of cerebral hernias and the accumulation of cerebrospinal fluid in the ventricles of the brain (hydrocephalus / dropsy of the brain):
- With the development of neoplasms and cerebral hernias, it is recommended to terminate the pregnancy. A fetus with such a pathology is usually not viable.
- Hydrocephalus, in most cases, occurs due to intrauterine infection. The infection must be treated with antibiotics without fail. If this treatment does not work, it is recommended to terminate the pregnancy. If there is no development of hydrocephalus, the fetus is usually allowed to be kept, but monitoring of its condition by ultrasound should be carried out constantly.
A decrease in the size of the fetal head may indicate an insufficient development of certain brain structures, or the absence of them. The absence of any brain structures is a strict indication for abortion, regardless of how long this pathology was detected.
Another reason for the decrease in BDP and LZR is a violation of the timing of fetal development. This phenomenon requires immediate medical intervention and correction, because. can lead to intrauterine death of the child.
BDP and LZR are the most significant characteristics that allow assessing the development of the brain, its individual structures and the fetus as a whole, throughout the entire gestation period.
Conclusion
For an adequate assessment of the information obtained by the fetometric method, it should be taken into account that the process of fetal development does not occur smoothly, therefore, deviations of certain characteristics are possible, which normalize over time. In addition, it is important to take into account the height of the baby's parents. A large fetus, as a rule, occurs in tall parents, the size of a baby of undersized parents may be somewhat lower than the above norms.
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Throughout fetal development, your baby is constantly growing. Growth rates slow down, then accelerate, but do not stop for a minute. An ultrasound examination helps to assess the dynamics of growth. And along with the many sizes of the fetus that are determined during this procedure, special attention deserves the circumference of the baby's abdomen or simply - coolant. Very often, women give this size an exaggerated value.
Measurement
The circumference of the tummy of the fetus begins to be measured not from the early stages, but only from the second trimester of pregnancy, when the tummy itself begins to be well visualized on the monitor of the ultrasound scanner. Size is a segment that the doctor visually lays along the line of the liver, stomach and umbilical vein.
Coolant is an important diagnostic indicator that is needed in order to assess the rate of intrauterine development and to identify intrauterine growth retardation of the fetus, if any.
The coolant itself is not very informative, and therefore it is customary to use the ratio of the length of the thigh to the circumference of the abdomen and the circumference of the head to the same coolant. It is in this capacity, supplementing the overall fetometric picture, that one can draw conclusions about how well and timely the development of the crumbs is.
Abdominal circumference gives a general idea of the state of the abdominal cavity and the estimated weight of the fetus (again, coupled with the length of the femur and the size of the head). Do not confuse the coolant with the volume of the abdominal cavity, the diameter of the tummy and the girth of the mother's abdomen. Very often, women looking for detailed information about the circumference of the tummy of the fetus, find articles in which all these concepts are mixed together.
Norms in the table
| Term in weeks | Circumference of the abdomen of the fetus, mm |
| 14 | 82–85 |
| 15 | 89–93 |
| 16 | 98–102 |
| 17 | 105–112 |
| 18 | 119–124 |
| 19 | 129–134 |
| 20 | 140–144 |
| 21 | 152–157 |
| 22 | 160–169 |
| 23 | 175–181 |
| 24 | 189–193 |
| 25 | 200–206 |
| 26 | 203–217 |
| 27 | 220–229 |
| 28 | 230–241 |
| 29 | 248–253 |
| 30 | 259–264 |
| 31 | 269–274 |
| 32 | 280–286 |
| 33 | 290–296 |
| 34 | 300–306 |
| 35 | 305–315 |
| 36 | 319–323 |
| 37 | 325–330 |
| 38 | 330–336 |
| 39 | 338–342 |
| 40 | 345–347 |
| 41 | 350–353 |
Reasons for deviations
If the lag and increase in the baby's tummy is insignificant, then no one will focus on this. We are all different, and the size of the abdomen is also directly related to our constitution and physique.
With a significant lag in the coolant of the fetus by weeks (by 2–3 positions in the table or by 2–3 weeks from the gestational age), they indicate a possible delay in the development of the fetus. With a significant excess of the size of the tummy, the reasons may lie in the irrational nutrition of the mother during pregnancy, in the presence of diabetes mellitus (including its gestational variety), in the edematous form of hemolytic disease of the fetus with a pronounced Rhesus conflict.
If the coolant is below normal, other fetometry criteria are also important, only in combination can it be established whether there is a developmental delay. It can be symmetrical (the most favorable form), or it can be asymmetrical, when only some parts of the body are reduced. Be sure to do an ultrasound with Doppler to assess the speed and quality of blood flow in the umbilical cord, placenta. This is important to find out if the baby is getting enough nutrition.
A woman is examined for virus carriers, infections. The reason for the decrease in the size of the tummy and, consequently, the estimated weight of the fetus, may be bad habits of the mother (smoking during pregnancy, drinking alcohol, drugs), poor nutrition, the presence of chronic diseases of the heart, blood vessels, kidneys.
Worry - in the sense of doing something - in both cases is necessary only when the results of ultrasound over several examinations do not fit into the range of normal values \u200b\u200b(are below the 10th percentile or exceed the 90th percentile).
The expectant mother may be offered hospitalization to treat the underlying cause that led to fetal malnutrition or hypertrophy. She will be injected with drugs that improve placental circulation. In the case of diabetes, a special therapeutic diet is recommended, and sometimes insulin.
Important! Often, a decrease or increase in coolant does not indicate a violation of the development of the crumbs, but that the term was set incorrectly. This is true for women with irregular cycles who do not remember the start date of their last period before pregnancy.
Self-deciphering the norms of fetometry by weeks is an occupation doomed to failure, especially in relation to the circumference of the abdomen of the crumbs, which is difficult to assess separately from other sizes. During pregnancy, children grow at different rates, sometimes their development is spasmodic, and therefore a decrease in the norm this week does not mean that in a couple of weeks the sizes will not become normal or will not exceed the norm.
Table of indicators of fetometry of the fetus - these are the norms of various sizes of an intrauterine developing child, determined by ultrasound. It was compiled on the basis of measurements carried out in a large sample and subsequent statistical analysis of the results. It is this table that is the basis for determining the gestational age.
In addition, by comparing the sizes obtained for a particular child with the norms, the symmetry of its development and compliance with the calculated gestational age are assessed.
How to prepare for the study
The measurement of an intrauterine developing baby is carried out during an ultrasound scan. This study can be performed both with a transvaginal sensor and through the anterior wall of the abdomen.
If the procedure will be carried out through the vagina, preparation for fetometry of the fetus is not necessary. If a transabdominal ultrasound is planned, then in the early stages of pregnancy you will need to before the examination, drink about half a liter of water an hour before the examination and do not go to the toilet after that.
This is necessary so that through a full bladder, as through a window, you can look into the uterine cavity. In terms of more than 12 weeks, this is no longer required, since the necessary “window” is created by amniotic fluid.
How is the procedure for measuring the parameters of the baby
A woman comes to the ultrasound room, where she undergoes a regular ultrasound examination - through the wall of the abdomen (then the stomach is lubricated with a special gel) or through the vagina (a condom is put on the sensor).
Which table will help you find out what period your baby corresponds to
The fetal fetometry data table consists of quite a few indicators. From 5 to 13 weeks, only three sizes of the fetus are evaluated by ultrasound:
- coccygeal-parietal size (CRL, KTR) is the maximum distance that can be measured from the head to the tailbone
- biparietal distance (BPD, BDP) can be measured from one to the other parietal bone, that is, we can say that this is the diameter of the head
- fetal egg (PY) is the volume of the cavity in which the baby develops; later, both the placenta and the waters around it will appear there.
| Term | ПЯ, mm | BPD, mm | CRL, mm |
| 5 | 5 | 1-3 | |
| 6 | 13 | 4-6 | |
| 7 | 21 | 3 | 8-10 |
| 8 | 29 | 7 | 14-16 |
| 9 | 36 | 10 | 22-23 |
| 10 | 44 | 14 | 31-32 |
| 11 | 51 | 17 | 41-43 |
| 12 | 57 | 20-22 | 42-73 |
| 13 | 63 | 24-26 | 51-87 |
This is how the ultrasound table of fetal sizes looks like, with which they are compared for compliance with the norm.
What parameters are evaluated from 13 weeks
The size of the child on ultrasound is estimated based on:
- OG - circumference (girth) of the head
- BDP - biparietal size (BPD), that is, the distance between the most distant points of the parietal bones from each other
- DB - femur in length
- LZR - fronto-occipital size, that is, the distance between the most distant points of the forehead and the back of the head
- OC - circumference (girth) of the abdomen
- SDJ - diameter of the abdomen in the anterior-posterior direction, that is, the sagittal size
- PJ is the diameter of the abdomen in diameter
- OG (or DRGK) - circumference (girth) of the chest
- DP - length of the humerus
- There are also lengths for the tibia, fibula, radius and ulna, and foot. Each of them has its own norm.
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44 questions about second pregnancy screening
You can evaluate pregnancy by fetometry by comparing the indicators indicated in the transcript of your ultrasound personally with the standard parameters in the available tables.
It is especially important to compare the BDP or the coccygeal-parietal distance - it is these 2 criteria that are fundamental for determining the gestational age by ultrasound.
| Term in weeks | LZD | BPD | OG | coolant | SJ | PJ | DB | DP | Dl.M.Bertz | Dl.B.berts | DgrK |
| 13 | 32 | 96 | 67 | 21 | 22 | 11 | 10 | 8 | 9 | 24 | |
| 14 | 35 | 26 | 106 | 78 | 24 | 25 | 15 | 13 | 11 | 12 | 26 |
| 15 | 39 | 32 | 118 | 89 | 28 | 29 | 18 | 17 | 14 | 15 | 28 |
| 16 | 43 | 35 | 130 | 100 | 31 | 32 | 21 | 20 | 17 | 18 | 34 |
| 17 | 47 | 39 | 143 | 111 | 35 | 36 | 24 | 23 | 20 | 21 | 38 |
| 18 | 52 | 42 | 155 | 122 | 38 | 39 | 27 | 26 | 2 | 24 | 41 |
| 19 | 56 | 44 | 168 | 132 | 42 | 43 | 30 | 28 | 25 | 26 | 44 |
Fetometry of the fetus at 20 weeks presents such indicators (data - in mm)
- BPR: 47-49
- OG:181
- DGRK: 48
- LZR: 60
- coolant: 143
- PJ: 46
- SJ: 45
- thigh length: 33
- normal length of the tibia: 29
- fibula length: 28
- shoulder length: 31
- length of forearm bones (radius/ulna) = 25/28
- the foot of a 20-week-old fetus is 33.
Fetometry of the fetus at 22 weeks is represented by such indicators in millimeters
- BPR: 54-56
- OG: 206
- DGRK: 53
- coolant: 165
- PJ: 53
- SJ: 52
- thigh: 39
- fibula/tibia (lower leg): 33/34
- shoulder: 36
- radius/ulna = 30/33
Fetometric parameters at 23 weeks (indicators in millimeters)
In the photo: an embryo on ultrasound at 6-7 weeks of pregnancy
- BPR: 57-59
- OG: 218
- DGRK: 56
- coolant: 175
- PJ: 55
- SJ: 56
- hip: 41
- drumstick = 35/36
- shoulder: 38
- forearm: 32/35
- height: 31 cm
- 580-600
Fetometry of the fetus after reaching 31 weeks (numbers are in mm)
- BPR: 80-82
- OG: 301
- DGRK: 81
- coolant: 258
- PJ: 82
- SJ: 81
- thigh: 60
- lower leg = 51/52 mm
- shoulder: 54
- forearm bones = 44/50
- height: 42 cm
- body weight: 1590-1690.
The norms of fetometry at 32 weeks on average look like this (mm)
- BPR: 83-85
- OG: 309
- DGRK: 83
- coolant: 266
- PJ: 85
- SJ: 84
- thigh: 62
- lower leg = 52/54
- shoulder: 55
- forearm bones = 46/52 mm
- height: 43
- weight: 1790-1890.
Fetometry of the fetus at 33 weeks can be presented in the form of such a table
Fetometric data at 34 weeks in millimeters
- maximum distance between the parietal bones (BDP): 89
- head girth (OG): 323
- chest across (DHRC): 88
- abdominal circumference (OJ): 285
- PJ: 91
- SJ: 90
- thigh: 66
- lower leg = 56/57 mm
- shoulder: 59
- forearm bones = 48/55
- height: 46-47 cm
- body weight: 2270-2390.
Ultrasound during pregnancy has long become an understandable and familiar procedure, because it is the simplest, most reliable and informative method for monitoring the condition of the fetus. As a rule, a specialist diagnostician during the study determines the duration of pregnancy, and almost every patient takes this for granted, without thinking - how exactly does the doctor determine the timing? And how accurate? What parameters does it use for this?
The role of ultrasound
It is diagnostics using ultrasound that helps the child's doctors on the basis of indicators of a very different nature, but at the same time directly established for a more informative result.
Setting an exact date also helps to predict the date of birth, which is very important both from a medical point of view and simply to calm the expectant mother. It is also necessary to know the most accurate period in order to control the development of the fetus, its condition, the correlation of norms with reality.
How does the specialist determine the timing?
Some patients believe that it is enough for the doctor to look at the image on the monitor - and the "age" of the child immediately becomes visually clear, but this, of course, is not so. The specialist fixes the obtained data of the embryo and compares it with the variants of the norm. Usually, to help the doctor, there are fixed indicators, where all the relevant norms are written for weeks.
Quantitative indicators.
Table No. 1. Norms of indicators at 5-10 weeks of pregnancy.
| KTP (Coccygeal-parietal distance) | Diameter of the ovum (average value) | Yolk sac diameter (mean) | |
| 5 | 2 | 18 | |
| 6 | 5 | 22 | 3 |
| 7 | 10 | 24 | 4 |
| 8 | 16 | 29 | 4,4 |
| 9 | 22 | 32 | 4,6 |
| 10 | 24-40 | 39 | 5 |
Table number 2.
| Gestational age (in weeks) | |||
| 11 | 17-21 | 10-16 | 52-73 |
| 12 | 22-24 | 17-21 | 58-83 |
| 13 | 25-27 | 23-28 | 73-95 |
| 14 | 28-30 | 27-31 | 84-110 |
| 15 | 31-33 | 32-39 | 110 |
| 16 | 34-37 | 41-49 | 111-135 |
| 17 | 38-41 | 45-54 | 122-149 |
| 18 | 42-47 | 48-59 | 131-160 |
| 19 | 48-49 | 52-63 | 142-174 |
| 20 | 50-53 | 56-67 | 154-186 |
| 21 | 54-56 | 61-72 | 167-200 |
| 22 | 57-60 | 65-76 | 178-211 |
| 23 | 61-64 | 68-80 | 190-223 |
| 24 | 65-67 | 71-85 | 201-236 |
Table number 3. Norms of indicators for the third trimester.
| Gestational age (in weeks) | BDP (biparietal size) (in millimeters) | Fronto-occipital size (in millimeters) | Head circumference (in millimeters) |
| 25 | 68-70 | 73-88 | 215-250 |
| 26 | 71-73 | 76-93 | 224-261 |
| 27 | 75-76 | 80-96 | 235-273 |
| 28 | 77-79 | 83-98 | 245-284 |
| 29 | 80-82 | 86-101 | 255-295 |
| 30 | 83-85 | 89-104 | 265-304 |
| 31 | 86-87 | 93-108 | 273-314 |
| 32 | 88-89 | 95-112 | 283-325 |
| 33 | 90-91 | 98-116 | 289-332 |
| 34 | 92-93 | 101-119 | 295-338 |
| 35 | 94-95 | 105-120 | 299-345 |
| 36 | 96-97 | 104-123 | 303-348 |
| 37 | 98-98 | 106-126 | 307-352 |
| 38 | 99-100 | 108-128 | 309-357 |
| 39 | 101-102 | 109-129 | 311-359 |
| 40 | 103 | 110-120 | 312-361 |
Table No. 4. Standards for the length of the fetus.
| Gestational age (in weeks) | Embryo dimensions (in centimeters) |
| 5 | 0,8 |
| 6 | 1,1 |
| 7 | 1,3 |
| 8 | 1,5 |
| 9 | 2,2 |
| 10 | 3,2 |
| 11 | 4,1 |
| 12 | 5,3 |
| 13 | 7,5 |
| 14 | 8,7 |
| 15 | 10 |
| 16 | 11,5 |
| 17 | 13,1 |
| 18 | 14,2 |
| 19 | 15,2 |
| 20 | 16,5 |
| 21 | 26,6 |
| 22 | 27,8 |
| 23 | 29,8 |
| 24 | 31 |
| 25 | 34,6 |
| 26 | 35,5 |
| 27 | 36,5 |
| 28 | 37,7 |
| 29 | 38,6 |
| 30 | 39,8 |
| 31 | 41,1 |
| 32 | 42,5 |
| 33 | 43,6 |
| 34 | 45 |
| 35 | 46,1 |
| 36 | 47,3 |
| 37 | 48,6 |
| 38 | 49,8 |
| 39 | 50,6 |
| 40 | 51,7 |
| 41 | 52 |
| 42 | 53 |
Table No. 5. Standards for the circumference of the abdomen of the embryo.
| Gestational age (in weeks) | Abdominal circumference (in millimeters) |
| 11 | 40-61 |
| 12 | 50-71 |
| 13 | 58-79 |
| 14 | 66-91 |
| 15 | 91 |
| 16 | 88-115 |
| 17 | 93-130 |
| 18 | 105-144 |
| 19 | 114-154 |
| 20 | 125-163 |
| 21 | 137-177 |
| 22 | 148-190 |
| 23 | 160-201 |
| 24 | 173-223 |
| 25 | 183-228 |
| 26 | 194-240 |
| 27 | 206-253 |
| 28 | 217-264 |
| 29 | 228-277 |
| 30 | 238-290 |
| 31 | 247-300 |
| 32 | 258-314 |
| 33 | 267-334 |
| 34 | 276-336 |
| 35 | 285-344 |
| 36 | 292-353 |
| 37 | 300-360 |
| 38 | 304-368 |
| 39 | 310-375 |
| 40 | 313-380 |
Table No. 6. Norms for the thickness of the placenta.
| Gestational age (in weeks) | Optimal placental thickness (in millimeters) |
| 20 | 22-23 |
| 21 | 22,8-23,5 |
| 22 | 23,6-24,4 |
| 23 | 24,5-26 |
| 24 | 25,3-25,8 |
| 25 | 26,2-26,7 |
| 26 | 27-27,5 |
| 27 | 27,9-28,3 |
| 28 | 28,7-29 |
| 29 | 29,6-30 |
| 30 | 30,4-30,7 |
| 31 | 31,3-31,8 |
| 32 | 32,1-32,5 |
| 33 | 33-33,4 |
| 34 | 33,9-34,3 |
| 35 | 34,7-35 |
| 36 | 35,6-36 |
| 37 | 34,3-34,7 |
| 38 | 34,1-34,5 |
| 39 | 33,8-34 |
| 40 | 33,5-33,7 |
What exactly is the specialist analyzing?
The analyzed indicators of the norm depend on the trimester and the specific period.
Particular attention is paid to the length of the fetus, since this is the only parameter that gives reliable information. During this period, there are no decisive differences in the development of embryos in different women, so ultrasound establishes the “age” of the child to the nearest day.
The second and , during which it is impossible to achieve absolute accuracy, because from this moment the embryos begin to develop individually. Doctors use average figures, but even in this case, the period is set as reliably as possible, and it is very possible to identify possible pathologies. At the same time, specialists analyze such indicators as the circumference of the child's head, the diameter of the chest, the coccygeal-parietal distance of the embryo.
Now it is necessary to analyze in more detail the meaning of the indicators presented in these tables, which may raise questions from patients.
distance, respectively, from the crown of the embryo to the coccyx. Thanks to this indicator, the most accurate determination of the term is possible, because these sizes are universal. Also, if there are factors preventing the setting of deadlines, KTR is the only reliable parameter in this case.
The diameter of the ovum is the directly fertilized egg from which the embryo will develop in the future. Its dimensions, of course, directly depend on the specific period and have long been studied - it is enough for the doctor to look at the corresponding table.
The diameter of the yolk sac is also an important indicator b, since the yolk sac plays a very important role throughout the development of the child (for example, in the first trimester it supplies the circulatory system of the embryo with nuclear erythrocytes). The dimensions are also always in the doctor's table. 
Between the parietal bones of the embryo.
Fronto-occipital size- the distance between the frontal and occipital bones, respectively.
Embryo length- is calculated when the child is in the most "unbent" state.
Placenta thickness- a lot depends on the placenta: it protects the child, and supplies him with everything he needs, and produces many hormones. Therefore, it is very important to check for compliance with its thickness to the standards laid down by the deadline. If the mother's condition is stable, there are no deviations - it is enough to simply establish the "age" of the embryo by the thickness of the placenta.
Accuracy
Many women are interested in - how accurate is ultrasound of the fetus? Therefore, it is important to note that ultrasound diagnostics establishes obstetric dates, in other words, the “age” of the embryo is calculated from the first day of the last menstruation. Sometimes a situation arises when a patient, referring to tables on the Internet and ultrasound results, finds differences in terms, so you need to know exactly which system was used to calculate, and not “sin” for the imperfection of ultrasound diagnostics.
Pathologies
Ultrasound of the fetus is informative not only as an aid to determine the period, but also in the detection of pathologies of a different nature. Moreover, some of them can only be detected using ultrasound, it is also important to note that, since this is a fairly effective method of monitoring the condition of the fetus.
So, the main pathologies that can be identified are:
- Developmental delay (detected by comparing normative parameters with reality, indicators below the threshold undoubtedly indicate the presence of an anomaly).
- Various defects (also found when indicators do not match).
- Low water.
- Polyhydramnios.
- Thickening of the placenta.
- indicators below the standards (especially the coccyx-parietal size) in the first trimester).
When can I go to the diagnostic room?
Of course, modern ultrasound technologies make it possible to detect an embryo already, but most clinics still do not have such perfect equipment. It is also important to note that this will require transvaginal ultrasound, which is very dangerous for the unborn child and can cause spontaneous miscarriage. So early examination can be done only if there are special medical indications, in any other case, you can be patient with knowledge of the exact date. 
It is advised to contact the diagnostician at the 5th week of pregnancy, when it will already be possible to examine the fetus in more detail using ultrasound, draw certain conclusions and set the period with maximum accuracy.
Is it dangerous?
Some patients refuse ultrasound diagnostics by both transvaginal and transabdominal methods, referring to the danger of ultrasound. Indeed, these fears are logical, because taking care of the health of the baby is characteristic of any mother. But for an embryo, even at a short time, there is no reason to believe that ultrasonic waves will harm the development of the child, cause pathologies or cause miscarriage.
Error Probability
Any woman can quite rightly consider that the size of the embryo is not the most reliable indicator for setting the term, because each child develops differently and it is difficult to determine its exact age. But in fact, over the years of medical practice, there can no longer be any doubt about the correctness of the period established on the ultrasound of the fetus.
If a woman still questions the results of an ultrasound scan, you can always carry out a number of additional diagnostic procedures, which in turn will allow you to determine the timing at the most accurate level.
Ultrasound of the fetus is not only a method for monitoring the condition of the fetus, controlling its development, but also quite reliable, accurate, informative, convenient and simple. » embryo, using special tables that a simple patient can rely on.
