Monthly PDR. How to calculate the date of birth: ways. Why DA setting results are considered approximate

In this article:

The expected date of birth begins to interest a woman from the first day she found out about her situation. The approximate birthday of a child can be calculated in several ways, but none of them can boast of 100% accuracy. Many factors can influence the pregnancy process, and delivery is often premature or late.

What determines the time of birth

Even in a healthy woman carrying a healthy baby, the date of birth may deviate from the approximately calculated period and depends on:

• on whether she gives birth in or;
• from the duration of the menstrual cycle;
• from heredity and other individual characteristics of the mother;
• on the characteristics of the intrauterine development of the baby;
• on how many babies are in the uterus.

In the presence of chronic diseases in a woman, a violation of the intrauterine development of a child, acute diseases or injuries during pregnancy, the delivery date may significantly deviate from the planned date.

Ways to determine the date of birth

The most common methods for determining the estimated due date are as follows:

• by the date of the last menstruation;
• by the time of ovulation;
• by date of conception;
• by ultrasound;
• according to the size of the uterus;
• by the first movement of the fetus.

Let's consider each in more detail.

By last menstrual date

The date of birth by menstruation is the most common way to determine.

It has been used by obstetrician-gynecologists for many decades because:

• not all pregnant women know the time of the last ovulation or the date of conception with regular sex life, but everyone remembers when they had their last menstruation;
• this is a pretty accurate method.

To determine the day of birth, it is necessary to remember the first day of the last menstruation, add 1 year to this date, then subtract 3 months, and then add 1 week. The calculated date will be a guideline for the expected birth. Another way to determine: add 9 months and 1 week to the first day of the last menstruation.

By time of ovulation or expected conception

The method of calculating the date of birth by the date of conception can be used with a planned pregnancy, when a woman specifically calculated the days of ovulation and knows them. It is during this period that conception occurs. 266 days are added to the first day of ovulation and the date of delivery is calculated according to the calendar. This method is called embryonic.

By date of intercourse

This method is convenient to use with irregular or rare sexual activity. In this case, the woman knows which day in her life was decisive. Everything is very simple - 266 days are added to this date. This method is closer to the embryonic one. The due dates calculated by these two methods may differ by only a few days because the date of intercourse and conception often do not coincide. Not everyone knows that some spermatozoa are able to live in a woman's body for up to 9 days, waiting in the wings.

According to ultrasound

Using ultrasound, the doctor can determine the approximate date of birth, based on the established age of the fetus. Most precisely, this is established in the first trimester of pregnancy. In the future, there may be an error from several days to 3 weeks.

According to the size of the uterus

An old medical method was an approximate determination of the gestational age and, accordingly, the expected birth according to the size of the uterus. As in the previous case, it is possible to more accurately set the time of delivery in the early stages of pregnancy. In the future, the size of the uterus depends on many factors (the size of the fetus, the amount of water). In addition, this method is only suitable if there is 1 child in the uterus.

By the first movement of the fetus

An old folk way of guessing the date of birth is to move the baby. After the disappearance of menstruation, a woman could only suspect that she was pregnant, but when the fetus began to move, this was a 100% sign.

The woman added 20 weeks to this date and could quite accurately guess the due date with minor errors. It should be borne in mind that multiparous are already familiar with the feeling of fetal movement in the uterus and they, as a rule, feel it 1-2 weeks earlier than primiparas.

Calculation efficiency

The exact day of delivery cannot be determined, because the period from 38 to 42 weeks of pregnancy is considered the normal period for delivery. Thus, as many as 28 days can be considered the date of delivery "at term". However, in the normal course of pregnancy, different methods of calculation approximately coincide and circle around the same date in the range of +/- 14 days.

Gynecologists officially still use calculations to determine the possible day of birth according to the last menstruation, so this period is called obstetric. This method in about 20% of cases guesses the date of birth with an accuracy of +/- 5 days, and this is a rather high percentage. The exact coincidence of the date of birth and the obstetric period is about 5%.

How do the features of the menstrual cycle affect the date of birth

Regardless of the duration of the menstrual cycle, the obstetrician-gynecologist applies the formula for calculating the term of childbirth by the date of the last menstruation. Accordingly, women with a short cycle and a long one will have the same due date. However, the date of ovulation is different for them, therefore, the conception and the term of delivery will be different.

With a short menstrual cycle (24 days) ovulation occurs on the tenth day. Fertilization occurs on the days of ovulation. Therefore, the actual due date in women with a short cycle will be expected a week earlier. The date of birth is calculated using the following formula: the date of the first day of the last menstruation plus 1 year and minus 3 months.

Long cycle (35 days) ovulation occurs on the twenty-first day. Childbirth will be a week later than the gynecologist calculated. A woman can calculate the date in this way: the date of the first day of the last menstruation, plus 1 year, minus 3 months, and plus 14 days.

Calculate the date of birth with an irregular menstrual cycle with large jumps should be according to the classical formula.

When you can not use the obstetric method of calculation

The obstetric method of determining the date of birth by the last menstruation is the most common.

But it is not possible to use it in the following cases:

• when pregnancy occurs immediately after a previous birth, and menstruation has not yet occurred;
• with severe menstrual irregularities, when the interval between menstruation can be more than a few months, as is the case with menopause or various female diseases, for example, polycystic ovaries or hormonal disorders.

What are the deviations from the deadlines?

The bearing of a child lasts 9 calendar months, or 10 lunar months (28 days each), or 280 days.

Births are classified into urgent, premature and late:

• Childbirth at 38-42 weeks is a normal period. Statistically, 70% of mothers give birth in the range of 39-41 weeks. Primiparas often give birth 1 week later than the normal due date. But with repeated births, on the contrary, women often give birth before 39 weeks.
• Childbirth after 42 weeks is late. The child is considered to be overdue. There are about 9% of such births.
• Childbirth before 38 weeks is premature. The viability of the baby depends on the gestational age at delivery. The closer this period is to normal, the better.

Everything is individual, and in case of premature birth, a completely healthy and mature baby can be born, more often this happens for a period exceeding 35 weeks. If the baby is underweight - less than 2500 grams, he will be considered premature.

The second degree of prematurity is established at the term of delivery from 32 to 35 weeks and the weight of the child is less than 2000 grams. However, he also has a very high chance of "ripening" and gaining weight after birth without the use of hardware life support.

In case of premature birth from 28 to 31 weeks, the child will be with prematurity of the 3rd degree and low body weight (from 1000 to 1500 g). Such children are successfully nursed in perinatal centers.

At the birth of a child for a period of 22-28 weeks, he will have a 4th degree of prematurity. The baby has extremely low body weight and undeveloped lungs. There is no surfactant substance, which ensures the free breathing of the child.

Previously, a fetus weighing 700 g was considered viable, now - with a mass of 500 g or more. Such children are nursed in intensive care units using special plastic transparent boxes - incubators, which provide the necessary temperature, humidity and sterility of the environment. The baby is connected to a ventilator, feeding is carried out intravenously or through a tube, the necessary drug therapy is provided.

A child born before 22 weeks will be unviable due to severe immaturity. Such babies are currently not able to leave the medicine.

Causes of preterm labor

The total share of all preterm births accounts for about 10% of cases. The cause may be maternal or fetal pathology, or a combination of various factors.

The most common of them:

• Social and domestic - smoking, alcohol abuse, drug use, stress, extreme physical activity, malnutrition and hypovitaminosis.
• Pathology of the uterus - the consequences of abortion, other operations on the uterus, hypoplasia, endometritis, endometriosis.
• Pathology of ongoing pregnancy - placental abruption, oligohydramnios, premature rupture of amniotic fluid, inflammation of the membranes, multiple pregnancy,.
• Mother's diseases - diabetes mellitus, hypertension, rheumatism, bronchial asthma, severe anemia, mental disorders, etc.
• Multiple anomalies in the development of the child, incompatible with life, at present, the latter is rarely the cause of premature birth, as women try to terminate their pregnancy in the early stages for medical reasons.

In the presence of such risk factors, a woman should be especially careful, since she has a high risk of having a premature baby. She may have to spend some time saving.

Determining the expected date of delivery is an important task. But in any case, the calculated period is approximate. It depends on many reasons. Therefore, with a long gestational age, a woman should listen to herself and expect childbirth, starting from the 37th week of pregnancy, or even earlier.

Useful video about calculating the due date

The article describes all the available ways to independently determine the date of the upcoming birth.

The emotional coloring of the news about the expectation of the baby begins to gradually lose its brightness and intensity, characteristic of the first days, and you return to a more or less normal state. The first thing that usually comes to mind is to find out when the baby will be born.

This quite natural desire is due to both practical goals and simple human curiosity:

• for someone interested in the month of the year to start shopping for appropriate clothes for the baby
• it is important for someone to choose a name for the child according to the laws of astrology or the church calendar
• for some, the estimated date is needed to plan the spouse's vacation

The reasons may be different, but information about when a woman is preparing for childbirth is of interest to many expectant mothers.

Toward the end of the third trimester, women usually begin to calculate the estimated date by all possible methods, double-checking it again and again, because they feel heaviness and fatigue, and they can not wait to meet their baby as soon as possible.

How to correctly calculate the due date? Table

Almost everyone knows that it takes nine months to bear a child. But how to count them correctly:

• from what day - sexual intercourse, ovulation, conception, implantation, last menstruation?
• months to take calendar or conditional for 30 days, how many days exactly in them?

When an expectant mother is faced with pregnancy for the first time, a period of nine months seems to be something very uncertain, and in order to calculate the date of birth as close to reality as possible, I want specifics.

The generally accepted method for determining the expected date of delivery (hereinafter - EDD) in order to monitor the development of the fetus and pregnancy in general is the countdown from the date of the start of the menstrual cycle.

EDD \u003d date of menstruation + 280 days (or 40 weeks)

This method sets the conditional boundaries of pregnancy, called obstetric period, which becomes a guideline for doctors and expectant mothers to monitor the development of the baby. When a woman is asked the question of how long she is, the pregnant woman will name exactly the obstetric week of pregnancy.

In fact, the true pregnancy came later than the date of the last menstruation by about two weeks, respectively, it lasts less than the obstetric period.

Why does the medical community resort to such a strange method of counting pregnancy from the day when it is still only in the plans of potential parents? To find an answer, let's briefly consider what happens in a woman's "pregnant" cycle and at what time:

1. no matter when intimacy took place, fertilization or conception will occur on the day of ovulation, and taking into account the vitality of spermatozoa, the difference between these moments can reach up to 5 days
2. ovulation occurs on average 14-15 days before the end of the cycle (next menstruation), but can occur earlier (16 days) and later (12-13 days)
3. conception does not guarantee pregnancy, for this a fertilized egg must attach to the uterus, or be implanted, which takes 6-8 days on average, but can also vary over time

IMPORTANT: 80% of conception cases end in unsuccessful implantation, that is, pregnancy does not occur, but the woman does not even know about it, since menstruation occurs on time.

So, it is very difficult to establish the starting point of pregnancy, due to the fact that it depends on several individual factors:

• cycle time
• day of ovulation
• duration of implantation

Even theoretically knowing exactly the date of pregnancy, this would not guarantee one hundred percent determination of the date of birth, since the onset of labor is also determined by many factors, including:

• physiological readiness of the baby
• the nature of the pregnancy
• mother's age and health
• number of previous pregnancies

For these reasons, doctors do not aim to accurately calculate the true date of conception and implantation. In addition, most women remember when they had their last menstruation, but not many people know what ovulation is and at what time it takes place specifically for them.

Therefore, it is much easier to count from the beginning of the cycle. This makes several assumptions:

• cycle duration 28 days
• ovulation occurs after 14 days (on the 15th day)
• timing of implantation fall within the normal range

If you fit into the specified parameters, you can safely look in the table below for the date of the proposed meeting with the baby. No one guarantees the exact probability, but this is the most approximate time.

• in the column on the left you should find the month in which you last had your period (indicated in black with an asterisk)
• then find in the line with this month the number (indicated in black) corresponding to the start date of the last menstruation
• under it, the estimated date of birth and the month will be indicated (indicated in crimson)

Examples shown in the table:

1. in a woman with the first day of the last menstruation on March 28, the birth is planned for January 2
2. if the beginning of menstruation was on August 11, replenishment should be expected on May 18

If your cycle is slightly different, the table will also be a good guide, but you need to be prepared for the fact that a run of 1-2 weeks is considered a normal option. In other words, from the point of view of medical science, the ideal pregnancy is 40 obstetric weeks, but more often falls in the range of 38-42 weeks.

IMPORTANT: According to the latest data, the range of variation between pregnancy durations of 37 days or 5 weeks is normal. Previously, this figure was 4 weeks (=42-38).

How to calculate due date by ovulation?

There are cases when a woman knows exactly the day on which she ovulated. This is usually typical for women who have been planning a pregnancy for a long time.

For example, ovulation became known using:

• Ultrasound, which a woman had several times during the cycle to monitor the maturation and release of the egg
• an ovulation test that shows a positive result 24-36 hours before ovulation
• basal temperature chart
• own explicit sensations due to long-term observations of your body

In these circumstances, I want to know the EDD more accurately, especially if the cycle does not meet the ideal standards both in terms of the total duration and the number of days in the second phase. The formula for calculating the day "X" in this case looks like this:

EDD = ovulation date + 266 days (or 38 weeks)

This period is called embryonic. If we compare these figures with the traditional formula described above, we get a difference of 14 days (= 280-266). Namely, on the 14th-15th day of the cycle, ovulation occurs in an average cycle of 28 days.

Recent studies by staff at the US National Institutes of Health concluded that pregnancy is more likely to be 268 days from the day of ovulation (rather than the accepted 266), that is, 38 weeks and 2 days. The duration of the gestational period also depends on how long it takes for the implantation of the fetus in the uterus. This point in the study was recorded on the first day of hCG growth.

IMPORTANT: It has also been found that the duration of pregnancy is affected by the age of the mother and her birth weight. The older the woman and the greater her birth weight, the longer the gestation period will be.

How to calculate due date from conception date?

Conception or fertilization occurs when the sperm and egg meet. Due to the fact that the egg leaves the follicle once a month (normally), which is called ovulation, and retains the ability to create a new life for only 24-36 hours, the meeting with the sperm and conception usually occurs on the day of ovulation or the next day.

Thus, the date of conception and the date of ovulation often coincide or differ by only 1 day. In this regard, the principle of calculating the EDD based on the date of conception is similar to the method based on the date of ovulation described above.

IMPORTANT: It is necessary to distinguish between the day of sexual intercourse and the day of conception. The difference between them can reach up to 5-7 days, depending on the lifespan of the sperm of a particular man.

How to calculate the due date exactly by menstruation?

The estimated date of birth, which the gynecologist will announce to the woman, as mentioned above, is based on data on the last menstruation. In this case, the day the cycle began is important, that is, the date on which the last menstruation began, the duration and end date do not play a role.

In order not to count 280 days from this date, there is an easier way (Negele's formula):

PDR \u003d date of menstruation - 3 months + 7 days + 1 year

Example #1:

• last menstruation was from 13 to 19 June 2015
• on the expected start date of the next cycle on April 10, menstruation did not start, and the pregnancy test was positive
• you should remember the date of June 13 (the beginning of the last menstruation), she will be asked from the pregnant woman more than once
• we return 3 months ago, we get March 13, 2015
• add 7 days, get March 20, 2015
• add a year, we get March 20, 2016 - this is the DA

IMPORTANT: In the formula, subtracting three months is equivalent to 92 days, so if the sum of the days in the months preceding the month of the last period is 89, 90 or 91 days, you should add not seven, but 4, 5 or 6 days, respectively.

Example #2:

• start date of the last menstruation - December 15, 2015
• subtract three months, we get September 15, 2015
• sum of days of subtracted months: november (30) + october (31) + september (30) = 91
• therefore, we add 6 days, we get September 21
• add year, DA - September 21, 2016

Example #3:

• date of menstruation - May 2, 2015
• minus three months - February 2
• sum of days in April, March and February (non-leap year) - 89
• so add 4 days to the result
• in the end, DA - February 6, 2016

How to calculate the date of birth with an irregular cycle?

The calculation of the due date used in medical practice is based on the assumption that a woman has a standard cycle with a duration of 28 days, in which ovulation occurs on days 14-15.

Let's imagine a situation:

• the date of the last menstruation of a woman is September 12, the EDD for menstruation is June 19 (September 12 + 280 days)
• day X comes, labor does not begin, the woman begins to worry, and the gynecologist insists on inducing labor, threatening the aging of the placenta
• and only in rare cases, the doctor will ask about the duration of her menstrual cycle
• meanwhile, the cycle of the expectant mother is 40 days, which means that the date of birth, for objective reasons, is shifted by at least 12 days
• ovulation, most likely, did not occur on the 14th day, but on the 26th day (= 40-14)

IMPORTANT: Usually the duration of the second phase of the cycle is stable and is 14 days, that is, ovulation occurs 14 days before the end of the cycle.

• in other words, conception occurred 12 days later than in the standard cycle (=26-14)
• accordingly, the woman has not yet “walked over”, the duration of her true pregnancy has not yet reached 266 days, there are no reasons for unrest

Thus, it is quite natural that childbirth has not yet occurred, and the explanation for this is logical: the woman had a late ovulation.

If you are the owner of a non-standard or irregular cycle (more or less than 28 days), it is better to focus on the date of ovulation and count from it (add 266 (268) days to the date of ovulation). If the date of ovulation is unknown, you should:

• find the difference between the number of days in your cycle and the standard
• if the cycle is more than 28 days, add the difference to the EDD calculated from the menstruation
• if the cycle is less than 28 days, subtract the difference from the EDD calculated from the menstruation

In the example above:

• the difference is 12 days =40-28
• cycle over 28 days
• therefore, a more likely due date is July 01 (= June 19 + 12 days)

How to correctly calculate the date of birth according to the first ultrasound?

To obtain more accurate results, ultrasound should be performed in the first trimester. If you apply too early, at 4-5 weeks, that is, immediately after the delay, there is no guarantee that the doctor will even see the fetal egg. Therefore, if there is no threat of ectopic pregnancy, you can sign up for an ultrasound scan after 6-7 weeks, and preferably in the period from 10 to 14 weeks.

With the help of ultrasound, the doctor will evaluate the coccyx-parietal size of the fetus, by which it is possible to determine the gestational age.

For example, if the CTE of the fetus is 44 mm, the gestational age on ultrasound is 11 weeks and 2 days (or 79 days).

The table indicates the obstetric period. Accordingly, 201 days (=280-79) or 28 weeks and 5 days remained until delivery.

In the 2nd and 3rd trimesters, the accuracy of matching the parameters of the fetus to the gestational age is significantly reduced, since the unborn baby begins to gain weight, grow and develop according to individual and genetic characteristics, which cannot be adjusted to any table.

How to calculate due date after IVF?

• Regardless of how the conception occurred: naturally or in the laboratory, the gynecologist will still focus on the PDR by the date of the last menstruation
• However, it is possible to calculate the embryonic period. The day of ovulation is taken as the day of puncture, when the woman took the follicular fluid with eggs. You can add 266 days to this date and get the DA
• The same result can be obtained by adding 14 days to the puncture date, that is, conditionally determine the date of the last menstruation, from which the obstetric period will be conducted, and counting 40 weeks (280 days)

How to calculate the date of birth by the first movement of the fetus?

Fetal movement, although quite specific and real, is a subjective factor in determining the date of birth.

The fact is that it is very difficult to determine when the expectant mother clearly experienced the presence inside the little man by his pushes and movements. Primiparous women notice this later than more experienced mothers, they are often confused with the processes taking place in the intestines, they think up something that they still cannot feel.

However, as a guide, this method can be taken into account. For this:

• 20-22 weeks are added to the period when the movement was first felt by the primiparous woman
• 24 weeks are added to the date of the first shocks that a multiparous woman felt

The different terms are explained by the fact that the first feel movements only at 18-20 weeks, and the second - from 16 weeks.

But this method can only roughly estimate the period of childbirth. At what point a woman will fix the first movement, it also depends on the structural features of the uterus, on the method of attaching the fetus to the wall of the uterus, on the sensitivity of the woman and many other factors.

How to correctly calculate the date of the second birth?

There is an observation that each subsequent pregnancy is shorter and lighter than the previous one. This is not always the case and depends on the individual. But often, nevertheless, the second birth occurs earlier, at 38 weeks, while the first - on average at 39-40 weeks. Otherwise, the calculation of the PDR is similar to the principle of determining the date of the first birth.

• It is known that the main guideline for calculating the EDD is the last menstruation, but there are frequent cases when a woman becomes pregnant again with a cycle not yet renewed after the first birth
• How to be in this case? A woman does not know the date of the last menstruation simply because they have not yet been after the first pregnancy
• In such circumstances, the period is usually set according to the results of ultrasound. This is the single most accurate way to determine the gestational age and calculate the due date. But it must be done no later than the 1st trimester.

How to determine the exact date of birth yourself: tips and reviews

1. If the menstrual cycle is 28-30 days, then the date of birth calculated in the antenatal clinic (by menstruation) will be the closest to the truth
2. If the cycle differs significantly in duration from the standard one or fluctuates from time to time by more than 3-4 days, inform the gynecologist about this when registering
3. In this case, keep in mind that labor may start before or after the due date by the number of days your cycle is shorter or longer than the standard 28-day period.
4. You should not get too hung up on calculating the date of birth, the percentage of exact hits is still not high
5. Prepare mentally in advance that childbirth may occur earlier or later than the due date
6. If the first birth occurred exactly on the due date, this does not mean that the same will be the case with the second
7. Remember that PDR is primarily needed for medical purposes: establishing significant abnormalities in the development of the fetus depending on the gestational age, assessing the maturity of the placenta and monitoring other vital signs in order to timely hospitalize the woman and stimulate delivery if necessary

Video: How to determine the date of birth?

It is useful for a woman who is about to become a mother to learn how to calculate the approximate date of birth from the known date of the last menstruation. These calculations, of course, will not be absolutely accurate, but knowing even the estimated moment of childbirth will allow you to calmly prepare for the upcoming process.

Calmness and balance are very valuable qualities for a pregnant woman, they should be armed and guided from the first to the last gestational week. The following material is about how the date of birth is calculated according to the last menstruation.

In contact with

Classmates

Based on the average duration of pregnancy (40 weeks), it is not difficult to calculate the date of birth from the last menstruation. For this, 40 weeks ahead according to the calendar are counted from the date of the beginning of menstruation.

In world obstetric practice, a quick method is used to calculate the duration of pregnancy and, accordingly, childbirth from this starting point - the date of the last menstruation. The terms of pregnancy determined by this method are called obstetric. They cannot be considered accurate, if only because no one can predict how many weeks the pregnancy will last - 36 or 42.

Obstetric calendar

The starting point in the calculation formula is precisely the first day of the last menstruation:

• from 1 day of the last menstruation, you need to count back 3 months according to the calendar;
• add 7 days to the received date.

1. My last period started on May 6th.
2. We count from May 6 3 months ago - we get February 6.
3. We add 7 days to February 6 - we get February 13.
4. The estimated date of birth, as it was possible to calculate by menstruation, is February 13.

This simplest calculation is called Naegele's formula, and its reliability correlates with the duration of the menstrual cycle. If the cycle is too long or irregular, counting errors are inevitable.

What affects the timing of childbirth?

The opinion of Western experts regarding the myths regarding the influence of certain factors on the date of birth is interesting. They conducted a study during which they gave daily urine tests to measure hormone levels. Thanks to daily monitoring, the dates of fertilization were precisely set in the subjects and the duration of gestation was calculated with maximum accuracy. As a result (after delivery), it turned out that the terms in some cases differed from those calculated by as much as 5 weeks, although the pregnant women were in the same conditions.

The most well-known factors influencing the duration of gestation and the date of birth:

• the duration of monthly cycles - it is believed that the longer they are, the later childbirth will occur;
• hereditary predisposition - in families where women overwear children, this feature is passed down from generation to generation;
• dynamics of intrauterine development - if the fetus develops “according to plan”, gains weight and height in time, the date of birth may coincide with the calculation for the last menstruation.

Experts criticized the myth about the effect of spicy food on the term of childbirth - if it was calculated by the date of menstruation, and childbirth does not occur, there is no need to “speed up” them by eating hot spices, as about 20% of pregnant American women do. In this way, they try to increase peristalsis (wave-like contraction of the walls of the stomach or intestines) and provoke uterine contractions, but this method is not scientifically substantiated.

The statement that the first births are usually delayed is also incorrect. Data from medical studies suggests that the first birth often occurs earlier than the date that the LC was able to determine from the last menstruation.

The sequence of births does not affect their timeliness.

Is it possible to determine exactly and what is the error?

Despite the fact that the Negele formula is considered an approximate way to find out the date of birth by the last menstruation, a considerable number of women on the forums claim that their children were born almost exactly on the date calculated by the doctor +/- 1-2 days. Is it possible, in this case, to consider this calculation method accurate if the statistics indicate only 5% of the coincidence of the date of birth with the one that could be calculated from the date of the last menstruation?

Most doctors generally suggest canceling the indication of the exact date of delivery in order to save expectant parents from completely vain anxiety about the “wrong” occurrence of true childbirth. This, according to experts, does not give anything but an extra reason for a stressful situation for a future woman in labor and her relatives.

As studies have shown, under the same gestation conditions, the time of onset of childbirth in different women can differ by 5 or even 6 weeks, that is, by 1.5 months.

How to calculate the due date in other ways?

In case of doubts about the date of the last monthly period of childbirth, it can be calculated in such ways as ultrasound, calculation for a gynecological examination, the appearance of the first movements of the fetus, and others. None of these methods guarantees the accuracy of the calculations.

How to find out by ultrasound?

When a woman passes in the early stages of pregnancy (11-12 weeks), the doctor determines the PDR based on the parameters of the fetus:

• the size of the fetal egg and embryo - is visualized as early as 4-5 weeks;
• coccygeal-parietal size (KTR) - the length of the fetus from head to tailbone;
• the size of the limbs, head and tummy of the baby, which up to 12 weeks develop approximately the same in all children.

According to these parameters, the gestational age is set, and based on this, the term of childbirth can be calculated, taking into account the approximate date of conception (usually 7-14 days from the first day of the last menstruation).

Calculation based on inspection

Surveys when registering a woman after a delay in menstruation also make it possible to calculate the date of birth. In this case, parameters such as (the most reliable) and the size of the uterus, determined during a gynecological examination, are taken into account. This is one of the oldest ways to determine the gestational age at the earliest stages (and, accordingly, childbirth).

By 5 weeks, the uterus softens, rounds and slightly increases in size. This is exactly how it is felt during a two-handed examination, when the obstetrician-gynecologist examines the state of the cervix through the vagina with one hand, and palpates the abdomen with the other, trying to detect an enlarged and rounded uterus.

After 12 weeks, the method of determining the period by examination is not used, since changes in the uterus vary depending on several reasons:

• the structure of the pelvis of the future woman in labor;
• the amount of amniotic fluid in the fetal egg (, and the norm);
• fruit sizes.

Upon receipt of examination data that differs from the calculations by ultrasound or by the date of the last regulations, preference is given to the latter when recording in the pregnant woman's card.

Manual examination of a pregnant woman

How to count on the first perturbation?

It is not recommended today to calculate the PDR by the appearance of fetal movements. Previously, they simply considered it - by the date when the child first moved, they added 20 weeks and got the estimated date of his birth. Long-term observations have shown the complete failure of this method, since the onset of fetal movements in different women varies markedly:

• some expectant mothers begin to "hear" the baby at 15-16 weeks;
• in others, movements begin after 20 weeks;
• working mothers who are in constant motion and bustle may not notice and miss the beginning of the first push;
• future women in labor, sitting at home and listening to every sound inside themselves, I can mistake intestinal peristalsis for movements.

Even mothers who have repeatedly given birth are not immune from imaginary sensations, so it is not advisable to calculate the date of birth by movements.

If the date of conception is known, and this is not always possible to know with high accuracy, calculating the due date is as simple as calculating the date of menstruation. To do this, you just need to count from the day of conception 40 weeks ahead or 3 months ago according to the calendar. But even this calculation cannot be called absolutely accurate, since it is impossible to predict the actual duration of pregnancy.

Child development calendar

In anticipation of childbirth, it is interesting to follow how the baby develops, how he prepares for the birth, according to the calendar of fetal development. The calendar is based on the materials of long-term observations of intrauterine development using various diagnostic tools.

Term	Fetal condition
1 trimester	By the age of 2 weeks, the fetus has the size of a grain of sand (0.35-1.00 mm), but already receives biochemical support, respiration and nutrition from the so-called extra-embryonic organs - the amnion, chorion and yolk sac. At 3 weeks, the heart, central nervous system, rudiments of bones and muscles, ears and eyes are formed, the growth of the embryo is 1.5 mm. 4-8 weeks is the most important and vulnerable period subject to harmful influences. The nervous system and other organs are actively formed, the heart begins to beat. The weight of the embryo reaches 3 g, the parieto-sacral size is 14-20 mm. At 8 weeks, the development period is called fetal, and the embryo becomes a fetus. His skin is still transparent, vessels are visible under it. The formation of the external genital organs begins, the tail disappears. At 10 weeks, the fetus already looks like a miniature replica of a human, albeit with a disproportionately large head and small limbs. Growth for the last 3 weeks has almost doubled - up to 60 mm according to KTR, weight - 8-14 g.
2 trimester	The facial features of the baby are rapidly taking shape, the “embryonic fluff” (the basis of future fingerprints), the fluff on the superciliary arches and on the head appears. The first taste sensations arise - the fetus reacts to bitter, sour and sweet substances dissolved in the amniotic fluid with swallowing movements. She knows how to yawn, suck her thumb and even somersault, but her mother does not feel it yet. When the obstetrician probes the mother's stomach, the fetus reacts - it frowns, turns its head. By week 16, the fetus acquires the following parameters: KTP - 108-116 mm, weight - 80-110 g. By the 20th week, the baby's movements become more active and tangible by the mother. He adds 10 g per day in weight, grows in length. At 22 weeks, it weighs 530-600 g, KTR - 21 cm, stores adipose tissue under the skin, becoming plump and less brisk than before.
3rd trimester	At 28 weeks, the fetus reacts to external sounds (music, mother's voice, etc.). “Trains” his lungs by swallowing amniotic fluid and making “breathing movements” with his chest. Its full height (from head to heels) is 38 cm, weight is 1.3 - 1.4 kg. By 30 weeks, wrinkles disappear from the baby’s face, there is already a decent “hair” on the head, which becomes proportional to the body, the weight reaches 1.8 kg, and the full height is 42 cm. At 31 weeks, the baby's immune system develops intensively, subcutaneous fat builds up. A surfactant appears in the lungs - a substance that will prevent the baby's lungs from sticking together after childbirth and ensure their functioning. The weight of the baby is approaching 2 kg, full height - up to 43 cm. 34 weeks - growth by leaps and bounds. Most babies turn head down in the uterus by this time. Weight approaches 2.75 kg, height - 46 cm. At 36 weeks, pregnancy status is defined as full-term, and delivery is expected any day. The baby's skin is cleared of vellus hair, the hairline on the head has grown to 1-2 cm, the nails have grown above the fingertips. In the intestines of the baby, meconium accumulates - a black-green substance that is the original feces. After birth, he immediately leaves the body of the child. In boys, the testicles have already descended into the scrotum, this will need to be checked immediately after the birth of the baby. The weight of the child reaches 3.1 kg, height approaches 50 cm.

The child development calendar shows that it is possible to calculate the date of birth by menstruation very conditionally - by the 36th week the child is ready for birth, but can remain in the womb for several more weeks. The reasons for the continued stay of the baby in the womb remain a mystery to medicine.

Conclusion

1. It is convenient and easy to calculate the date of birth by the terms of the last menstruation - you need to subtract from the last 3 months and add 7 days.
2. For many women, the dates calculated by the obstetrician coincide with the actual dates of birth.
3. The starting point in the calculation is the first day of the last menstruation, so it is advisable to remember or write down the timing of their appearance.

In contact with

Date of birth: are there exact methods for determining it?

The date of birth is the main thing that worries women who are carrying a child under their hearts. Every pregnant woman wants some certainty. Only after learning about the onset of a long-awaited pregnancy, the expectant mother wants to know the date of the expected birth. But how to do it right? Many women try to calculate the due date from the date of conception. And they do it in a not entirely correct way, adding 9 months to the estimated date of conception to calculate the date of birth. But this way of determining the date of birth by the date of conception is not entirely correct. Pregnancy does not last exactly 9 months, but 280 days (10 lunar months). So how to correctly determine the date of birth by the date of conception? Are there other methods for determining the due date? Which one is the most accurate?

Determination of the date of birth by the date of conception and the day of ovulation.

The date of birth by the date of conception is determined quite simply. As you know, the female body is capable of conception only during the period of ovulation - the release of a mature egg from the ovary. The female menstrual cycle lasts, on average, 28-35 days. And ovulation occurs in the middle of the menstrual cycle. Knowing the date of your ovulation, you can easily predict the date of birth. Some women feel their ovulation. During this period, they feel stabbing or aching sensations in the lower abdomen, the amount of vaginal discharge increases, sexual desire increases, and some even begin mild spotting (bloody) discharge from the vagina. Ovulation is accurately determined by ultrasound. But how to determine the date of birth, if you don’t know exactly the day of ovulation? To do this, you can simply calculate the middle of your menstrual cycle and add 280 days to this day. Thus, you will calculate the approximate date of delivery by the date of conception. For example, if your menstrual cycle lasts 28 days, then ovulation occurs somewhere on the 12th-14th day of the cycle. Add 10 lunar months (280 days) to the date of the proposed conception, and get the approximate date of birth. If you calculate the date of birth by the date of sexual intercourse, then this option is even more reliable, especially if the sexual intercourse in the last menstrual cycle was single. But, it is worth remembering that the date of conception may not coincide with the day of sexual intercourse. Spermatozoa can "live" in the female body for up to several days. That is, if unprotected intercourse occurred on the 10th day of the cycle, then ovulation and conception could occur on days 12-13. And you need to calculate the date of birth based on the date of conception, that is, starting from the day of ovulation.

Determination of the date of birth, based on the date of the last menstruation.

Coming to a consultation with a gynecologist, usually the first thing the doctor asks is when was the last menstruation. Young inexperienced girls, for the most part, do not particularly monitor the regularity of their menstrual cycle and cannot name the exact date. Others begin to remember the date of the beginning and end of menstruation. Although the doctor needs to know only the day of the first day of your period to determine the gestational age and the date of the expected birth. It is from this day that the menstrual cycle is counted and its duration is calculated.

The simplest formula used by gynecologists themselves to determine the date of birth is the Negele formula. In order to calculate the date of birth from it, you need to subtract three months from the first day of your menstrual cycle and add seven days. For example, your last period started on April 3rd. We subtract three months - it turns out January 3. Now we add 7 days to January 3rd. It turns out January 10 - this is the expected date of birth.

But this method of determining the date of birth is far from always highly accurate. Since it is calculated to determine the approximate date of birth for women whose menstrual cycle is exactly 28 days. If it is longer, then the date of birth is likely to come a little later and vice versa. This is due to the fact that with a long menstrual cycle, ovulation occurs later, and with a short one, earlier than 12-14 days, with the calculation for which this formula is derived. With an irregular menstrual cycle, it is generally very difficult to determine the date of ovulation and use this method to determine due date considered incorrect.

Determination of the date of birth using ultrasound.

It is considered the most accurate to determine the date of birth using ultrasound in the early stages of pregnancy, up to 12 weeks. Having passed an ultrasound at a very early date, you can find out the duration of your pregnancy with an accuracy of literally up to one day, and in accordance with this, calculate the approximate date of conception and the date of birth.

The gestational age is put on ultrasound and at later stages of pregnancy, in accordance with the size of the head and limbs of the fetus. But the conclusion of such an ultrasound can no longer be taken as the basis for determining the date of birth, since all children develop in their own way, individually. And some children are born weighing 5 kg, and others - 3 kg. Both of these are the norm. But only in the first case, a woman on an ultrasound scan in the second and third trimester of pregnancy will be given a period of a couple of weeks more than the present and, accordingly, the date of birth will be set earlier. Childbirth, most likely, will begin later, and doctors, and the woman herself, will rush things, thinking that the pregnancy is overdue, and the expected date of birth has already passed. And vice versa, short, thin parents give birth to children with the same constitution. And on ultrasound, a woman is diagnosed with “intrauterine growth retardation” or simply put the gestational age less than it actually is, thereby pushing back the correctly set date of birth to a later date.

Setting the approximate date of delivery based on the results of a gynecological examination.

A gynecologist conducting a manual examination of a woman's genitals can determine pregnancy "by touch". The gestational age can be set absolutely accurately, starting as early as 3-4 weeks. It is worth knowing that at later dates (more than 12 weeks) it will be almost impossible to set the exact gestational age and determine the approximate date of birth. The reason for this is the same as when performing ultrasound in the later stages - this is the fact that each child develops in his own way, individually. So, what does the gynecologist pay attention to during the examination? First of all, it is the size and shape of the uterus. In pregnant women, the uterus acquires a spherical shape (in non-pregnant healthy women, the uterus is pear-shaped) and increases in size. A more or less experienced gynecologist sets the gestational age and approximate due date based on the size of the uterus.

Determining the date of delivery in later pregnancy.

There are times when it is difficult to determine the date of birth by the date of conception. In such cases, you can use such a proven technique as determining the date of birth by the date of the first movement of the baby.

The baby in the womb begins to make its first movements quite early, about 12 weeks. But a pregnant woman does not feel them, since the baby is still very small. A primiparous woman begins to feel real movements at a period of 20 weeks, a multiparous woman at 18 weeks. Thus, to calculate the date of birth, in the first case, 20 weeks must be added to the day of the first movement, in the second case - 22 weeks. Thus, we will get an almost exact date of birth. Many women say that they begin to feel the first movements much earlier than the due date - at 16 or even 14 weeks. Gynecologists usually do not take such statements seriously, attributing the baby's movements to intestinal contractions. But such sensitive women still occur and, in their case, determining the date of birth by the date of the first movement of the baby will be incorrect.

Somewhere from 14-16 weeks of pregnancy, a gynecologist can accurately determine the gestational age and the approximate date of delivery using an ordinary examination (not on a gynecological chair). By touch, he will determine the height of the bottom of the uterus, on the basis of which it will be possible to judge the gestational age and calculate the date of birth not by the date of conception. At 16 weeks, the bottom of the uterus is located between the pubis and the navel, at 24 weeks - in the navel area, at 28 weeks - 4-6 cm above the navel, etc. There is another method for determining the gestational age and date of birth - measuring the circumference of the abdomen. But it does not differ in accuracy, since we are all different and the waist size is initially different for all of us. In women who are prone to fullness, the volume of the abdomen will, in any case, be larger than that of a thin woman who was given exactly the same date of birth. Measuring the length of the uterus is much more informative for calculating the date of the upcoming birth.

Why is the date of birth called not exact, but only approximate?

Indeed, it is not possible to calculate the exact date of birth even by the date of conception. The reasons for the errors in calculating the date of birth by conception, we considered at the beginning of this article. A relatively small percentage of women give birth exactly on the date determined by the gynecologist. Although they say that pregnancy should last exactly 40 weeks, but in many cases this is not the case. The date of birth can come at 38 weeks and this is also not a pathology. With multiple pregnancies, childbirth almost always occurs earlier than the date determined by the gynecologist. Some other factors, such as polyhydramnios, high blood pressure in a pregnant woman, diabetes, etc., may also affect the date of birth, or rather its onset. You can calculate the date of birth by the date of conception using an online calculator.

30.10.2019 17:53:00

Determining the gestational age and the estimated date of birth is very important for both the woman and the doctor leading her. Many laboratory and instrumental studies are prescribed precisely at the time when it is easiest to identify the pathology in time. Comparison of fetal parameters with the average statistical indicators of each period of pregnancy helps to identify and correct underdevelopment. Clarity in determining the date of birth of a child allows you to carefully prepare for this event and open a sick leave in time so that the woman has time to gain strength before childbirth.

There are several methods to help calculate the required indicators. An obstetrician-gynecologist uses them in combination, since almost every method has an allowable error associated with subjective reasons: the individual characteristics of a woman, elementary forgetfulness - it is difficult to remember the date of the last menstruation. The term of the expected birth can be determined quite approximately, since a full-term pregnancy lasts from 38 to 42 weeks, and this is normal from the point of view of physiology.

Calculate

Negele formula

The method of calculating the due date using this formula is great for women with a regular standard cycle lasting 28 days. Negele's formula is simple - to determine the desired date, you need to subtract 3 months from the first day of the last menstruation, and then add 7 days to the resulting figure. If the menstrual cycle was constant, but lasted more or less than the standard one, the difference between your own and the standard cycle should be added to the date obtained, or the same number of days should be subtracted.

How to calculate due date based on ovulation date?

If a woman in the month preceding conception determined the onset of ovulation by basal temperature, this will help to accurately determine the gestational age. Conception occurs on the day of ovulation, when the egg ready for fertilization leaves the ovary. If sexual intercourse took place 1-2 days before ovulation, spermatozoa remain ready for fertilization all this time, that is, conception can occur a short time after sexual contact. If you add 38 weeks, or 266 days, to the date of ovulation, you can find out the estimated date of birth of the child.

If a woman does not know when she ovulated, but has a stable 28-day menstrual cycle, it is assumed that conception occurred in the middle of the cycle, that is, on day 14. With an irregular cycle, this method has an error.

We determine the date by the movement of the child

The date when a woman first felt the baby move is very important for correcting a comprehensive calculation of the term of the expected birth. Although the fetus begins to move as early as the twelfth week, for the first time most women feel these gentle movements in the middle of the gestational period, that is, in the twentieth week. However, this rule does not apply to everyone - during the second and subsequent pregnancies, a woman may feel the first movements 2 weeks earlier.

A primiparous woman of a fragile physique also has such an opportunity, while a pregnant woman with a solid build feels movements later. These sensations can be called subjective, because they depend on the woman's sensitivity to what is happening in her body. The thickness of the myometrium also affects the severity of the movements of the child.

All these nuances mean that the above method of determining the date of birth cannot be considered the main one, it is used only in combination with other methods.

How do obstetricians-gynecologists calculate the gestational age?

When calculating the gestational age, the doctor usually relies on the start date of the last menstruation, however, the main calculations are carried out taking into account a complex of various criteria.

According to the size of the uterus

In the early stages of pregnancy, when individual differences in fetal size are not yet apparent, it is possible to determine the date of delivery using this technique. For a period of 4 weeks, the size of the uterus is compared with a chicken egg, for a period of 8 weeks - with a goose.

From the twelfth week, this method is already difficult to apply, since in the future the parameters of the uterus and fetus differ in different women with the same period.

According to ultrasound

The method of determining the date of birth according to ultrasound scanning is valid at the beginning of the gestational period, more precisely, until the third month. After twelve weeks, it is impossible to accurately determine the date of birth based on ultrasound data due to individual differences in fetal parameters in women of different constitutions.

According to the height of the fundus of the uterus

This method has been used by the obstetrician-gynecologist since the beginning of the second trimester. The longer the fetus develops, the higher the bottom of the organ becomes, which rises beyond the small pelvis.

The height of the fundus of the uterus is determined when the woman is lying on her back. The doctor carefully palpates the abdomen and measures the distance from the pubic symphysis to the fundus of the uterus. This indicator increases evenly throughout the gestational period, and immediately before childbirth, the uterus descends.

When using this technique, an error of 2-3 cm is laid. It can be caused by polyhydramnios, pregnancy with twins or triplets, the age of the woman, and the size of the fetus. To clarify the indicators, the waist circumference of the pregnant woman and the parameters of the fetus are taken into account.

Calculation of the height of the fundus of the uterus by week:

8-9 weeks - height 8-9 cm, the uterus is still located within the small pelvis;

10-13 weeks - height 10-11 cm, the uterus increases, the placenta develops intensively, the fetal cardiovascular system begins to work;

16-17 weeks - height 14-18 cm, the uterus is located between the navel and the pubic joint, the fetus looks like a little man, all of whose organs are already laid;

18-19 weeks - height 18-19 cm, the unborn child develops arms and legs with fingers, the cerebellum, the immune system, the placenta fully assumes the responsibility for ensuring the functioning of the fetus;

20 weeks - the height of the uterus in centimeters corresponds to the gestational age in weeks;

21 weeks - height 21 cm, from now on the height of the uterus will increase by 1 cm weekly, now it is 2 fingers below the navel.

22-24 weeks - height 22-24 cm, the bottom of the uterus at the level of the navel, easily determined by palpation, the body weight of the fetus is 0.6-0.7 kg;

25-27 weeks - height 25-28 cm;

28-30 weeks - height 28-31 cm;

32 weeks - height 32 cm, the upper edge of the uterus is located between the xiphoid process of the sternum and the navel;

36 weeks - height 36-37 cm, the uterus is palpable at the line of connection of the costal arches;

39 weeks - height 36-38 cm, the uterus begins to descend, the weight of the fetus exceeds 2 kg;

40 weeks - the height of the uterus decreases to 32 cm, it is again between the navel and the ribs, the child is ready for delivery.

Head size and fetus length

To calculate the gestational age, the following methods are used:

Jordanian method. The term is calculated according to the formula X=L+C, where X is the term in weeks, L is the length of the body of the fetus (cm), C is the diameter of its head (cm).

Skulsky method. Here the formula is: X = (L x 2) - 5/5, where L is the length of the fetal body (cm), the number 5 in the numerator of the fraction is the thickness of the myometrium, the number 5 in its denominator is a special coefficient.

Any calculations are only an approximate guideline. According to medical statistics, only 10-17% of babies are born on time, the rest are born earlier or later than the expected date. This circumstance is influenced by many factors: heredity, pregnancy pathologies, stressful situations and other reasons.