Estimated due date. Calculation of due date. By last menstruation

Almost every pregnant woman is very interested in when her baby will be born. There is no exact method for determining the day of birth. But there are quite a lot of methods that allow you to calculate the estimated date of birth (EDD). How to use these methods, and which one is the most accurate? More on this later!

Determining the date of birth based on the date of conception

Based on the date of conception, you can determine the approximate birthday of the baby. It is known that conception of a child can only occur during the period of ovulation, i.e. at the time when the finished egg leaves the follicle and goes to meet the sperm.

As a rule, ovulation occurs on the 14th day of the menstrual cycle. The menstrual cycle should be understood as the period of time from 1 day of menstruation to 1 day of the next. The duration of this cycle is individual for each woman. On average it is 27-29 days, but can stretch up to 35 days or even more.

Women who carefully monitor their menstrual cycle and plan a pregnancy are usually able to determine their ovulation day.

Knowing the date of ovulation, you need to add 280 days to it(which is how long pregnancy lasts on average for women). You can find out the expected date of birth of a child using this method only if you have a regular menstrual cycle.

At the same time, you need to understand that the day of sexual intercourse is not always the day of conception, because The lifespan of sperm can reach 3 days.

Calculation of due date based on last menstruation

The approximate birthday of the baby can be calculated based on the last menstruation. You need to know the day it starts. To determine the approximate date of birth of a child count forward 280 days from the first day of your last period(average duration of pregnancy).

According to statistics, no more than 5% of children are born on the “calculated” day. About 85% of babies are born with a deviation of 5-7 days from the calculated MPD, and the remaining babies are “in a hurry” or “late” for another week. According to medical standards, the normal duration of pregnancy is 38-42 weeks, and not strictly 40 weeks, as many people mistakenly believe for some reason.

At the same time, the duration of pregnancy can be influenced by a variety of factors, including the individual speed of development of the child and the duration of the menstrual cycle of the expectant mother.

For example, if the cycle lasts up to 24 days, the baby may be born 1-2 weeks earlier than the due date calculated using the formula mentioned above. If the duration of the menstrual cycle exceeds 32 days, the child may be “late” for the same 1-2 weeks, but such a “delay” will not be considered postmaturity.

How to calculate the due date using ultrasound

Currently, the method of calculating the date of birth using ultrasound is the most reliable. You just need to pay attention to the period of pregnancy during which the study is performed.

For example, if an ultrasound is performed at 11-14 weeks of pregnancy, the expected date of birth can be determined with an error of 1-3 days.

In the first trimester of pregnancy, embryos practically do not differ in size. During the second trimester, differences in the weight and height of the fetus can be quite significant, and in the third trimester they become even more pronounced. Therefore, during the 2nd and 3rd trimester, it is unlikely that it will be possible to find out at least the expected date of birth using ultrasound.

At the first move

At a time when medicine did not yet have the means to conduct ultrasound examinations, the most reliable way to determine the expected date of birth was the method of determining the baby’s first movement.

Doctors today ask pregnant patients about the date of the baby’s first movement and note this information on the exchange card, but such importance is no longer attached to this day. But no one is stopping you from trying.

According to this method, women who are pregnant for the first time most often feel fetal movement at the 20th week of pregnancy. Hence, to the day of the first movement you need to add the same number of weeks. This will determine the expected date of birth.

In the second and subsequent pregnancies, the first movements may appear as early as the 18th week. To determine the expected date of birth in such a situation, you need to add 22 weeks to the day of the first movement.

This method can hardly be called the most accurate. Due to individual physiological characteristics, some pregnant women feel fetal movement earlier than the specified period. In addition, many modern mothers lead an active lifestyle, against the background of which the moment of the first movement may simply not be noticed.

If a woman is forced to adhere to bed rest for medical reasons, she will probably feel the fetus moving. Moreover, the first movements can be noticed by such women even before the 18th or 20th week.

Based on the results of a gynecological examination

During a gynecological examination, the specialist notes the degree of enlargement of the uterus. In accordance with this indicator, you can quite accurately determine the approximate day of birth. The uterus increases in size along with the fetus, which is why an experienced specialist in most situations can calculate the approximate date of birth without any problems.

Based on the size of the uterus during the first trimester of pregnancy, the doctor can find out the duration of pregnancy and thereby calculate the approximate date of birth, using the approximate day of the last menstrual period in the calculations.

In the 2nd and 3rd trimesters, it is very difficult to establish the date of birth based on the results of a gynecological examination, because In different women, the size of the uterus changes at different rates. In view of this, this method is considered ineffective in late pregnancy, and therefore is not used.

According to the results of obstetric examination

In the second half of pregnancy (usually starting from the 20-21st week) during each gynecological examination doctor measures pregnant woman and the height of the fundus of her uterus. Thanks to these measurements, the specialist has the opportunity to monitor the progress of pregnancy and timely determine the presence of any kind of deviations from the norm. Also, thanks to this information, the doctor can approximately calculate the due date.

However, you cannot completely trust this method either, because... the accuracy of the readings obtained as a result of an obstetric examination may depend both on the individual characteristics of the pregnant woman’s body and on the accuracy of the doctor.

Which method is the most effective?

The most effective method for determining the expected date of birth is ultrasound. Also, the method of counting from the date of the last menstruation shows relatively high accuracy. It is very good if the results of calculations using these two methods coincide - then the chances of the baby being born on the expected day will also increase.

But if the dates do not coincide, there is no need to be upset. Carefully monitor the course of your pregnancy and undergo regular examinations. Remember: each of the methods discussed allows you to determine only the approximate date of birth.

Why are the results for determining the due date only approximate?

In reality, it is almost impossible to determine the exact birthday of a child. Only a few women manage to give birth exactly on the day specified by the doctor or on their own. Most often, pregnancy lasts 280 days (40 weeks), but often mothers give birth at 38 weeks or even earlier, and in many situations this is considered normal. Moreover, if a woman is pregnant with more than one child at once, then, in most cases, she will begin giving birth earlier than the date set by the gynecologist.

It is important to understand that a baby can be born 1-2 weeks later than the due date - in most situations this is not considered a deviation.

That is, a deviation from the “standard” 40 weeks by 1-2 weeks forward or backward is not considered something abnormal.

It is also important to understand that the duration of pregnancy and the approximate day of birth can be influenced by a variety of factors. For example, various diseases and complications can lead to premature birth.

Thus, in the absence of complications, the child is born only fully mature and ready for life outside the mother's womb. It is almost impossible to accurately calculate the due date. But the above methods, as well as our online birth date calculator, will help you determine the expected or approximate date of birth.

Health to you and your baby!

Pregnancy is one of the most exciting and at the same time responsible periods in the life of every woman, and therefore it is not at all surprising that each of us wants to know the date of birth as soon as possible. However, this issue often causes numerous disagreements and disputes. Expectant mothers “torture” doctors with their questions, because they want to prepare for an important event, but they just shrug their shoulders, because they are not able to accurately determine the date of birth of the long-awaited baby.
In order to Calculate the due date, click the “find out due date” button.

Today: 27.07.2019
Date of the first day of last menstruation:
Conception most likely occurred (+-2 days):

Estimated due date:
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The estimated date of birth (EDD) is calculated in several ways, each of which is approximate. That is, if according to calculations the baby should be born on January 1, then it is not a fact that this will happen with one hundred percent accuracy on this very day. Very often there are deviations from the expected date in one direction or another. And labor can begin either 2 weeks earlier or later. I bring to your attention a fairly simple, but very effective way to find out the probable due date of a child, which has been successfully used by many doctors in clinics for quite a long time.

Calculation based on the last day of menstruation

4 Alternative Ways to Calculate Due Date

• 1. You can find out the due date with fairly high accuracy by visiting a gynecologist’s office. The doctor will not order any tests for this, he will simply measure the size of the uterus, which will increase in size according to the age of the fetus. However, this method of calculating the date of birth of the baby is effective only in the first trimester of pregnancy. In the later stages (in the 2nd and 3rd trimester) in each woman, an increase in the size of the uterus occurs with varying intensity, depending on the individual characteristics of the body.
• 2. You can calculate the date of birth based on ovulation, which is the most favorable period during which conception most likely occurs. On such days, a woman usually experiences increased sexual desire. In addition, her discharge (cervical fluid) becomes stickier and thicker, basal body temperature rises by several tenths of a degree, the cervix rises, and the mammary glands become dense and painful.

• 3. Hardware calculation using ultrasonic waves can also be considered one of the most effective methods that allow you to determine the due date with an accuracy of 1-3 days. The most accurate calculations will be if an ultrasound is done during the 11-14 weeks of pregnancy.
• 4. His first movement, which usually occurs at the 20th week (for first-time mothers) and at the 18th for the second and subsequent pregnancies, will help declassify the secret of your child’s date of birth. In ancient times, when there was no ultrasound, this method of calculating the due date was almost the only one.

The effectiveness of hardware methods in calculating the due date

Is deviation from the deadline normal?

How do the characteristics of the menstrual cycle affect the date of birth?

The duration of pregnancy from conception to birth of the child is about 266 days, or 38 weeks. Since the date of conception is usually unknown with certainty, in modern obstetrics it is customary to calculate the gestational age from the first day of the last menstruation. With this calculation, it is approximately 280 days, or 40 weeks, since ovulation (the release of a mature egg from the ovaries) and, accordingly, fertilization usually occurs approximately two weeks after the start of menstruation. When turning to an obstetrician-gynecologist, many expectant mothers begin to worry about the difference in the date of birth - the one calculated by the doctor and the one expected by the woman herself. In order not to worry in vain, you need to know that there are two stages of pregnancy - obstetric and embryonic.

Embryonic term- this is the true gestational age from conception; it usually lags behind the obstetric one by about 2 weeks.

Obstetric term Doctors determine from the first day of the last menstruation before pregnancy. It should be remembered that all doctors use it: the size of the fetus, the timing of examinations, maternity leave and the date of birth are calculated taking into account only the obstetric gestational age. It is also very important to know the exact gestational age for conducting screening tests for the presence of genetic abnormalities in the fetus (ultrasound and blood tests), since these examinations are carried out at strictly defined periods of pregnancy.

During the first visits to the antenatal clinic, the obstetrician-gynecologist usually determines the expected date of birth (ED). Several methods are used for this.

Method 1. Method for determining the date of birth based on the date of the last menstruation

This is the most common method of calculating the maximum allowance. To calculate the date of birth, three months must be subtracted from the date of the last menstruation. You need to add 7 days to the resulting date - this number is the expected date of birth. Obstetricians-gynecologists, when calculating PDR using this method, usually use special obstetric calendars, which greatly simplify the calculations.

However, it is not always possible to accurately calculate the MDR using this method alone. This happens in cases where a woman has irregular menstruation, or in those patients who have a regular but long menstrual cycle. For example, if a woman has a normal cycle length of 35 days (and not 26-28, as for most), then, most likely, she will be able to conceive only around the 21st day of the cycle (and not on the 14th, as with a 28-day cycle). Accordingly, the PDA calculated by menstruation will be a week earlier than the actual expected date of birth.

Method 2. about the date of ovulation or date of conception

If the date of conception is reliably known, then you can calculate the expected date of birth yourself by adding 266 days - this is the average gestation period. But there are some nuances here too. You need to understand that even if a woman knows exactly the date of ovulation or the date of sexual intercourse after which pregnancy occurred, this does not mean that she absolutely knows the date of conception. A sperm that enters a woman’s body is capable of fertilization on average within 4–5 days, sometimes even within a week, and a mature egg retains the ability to conceive within 2 days after ovulation. Therefore, even knowing exactly the date of sexual intercourse or ovulation, one cannot say with certainty that fertilization occurred on that day. It could have happened later. Therefore, the period calculated from ovulation or the date of conception cannot be considered absolutely accurate.

Method 3. Method for determining the due dateupon first appearance at the antenatal clinic

Typically, the date of the upcoming birth and the gestational age are calculated by the doctor when registering for pregnancy. Doctors call this calculation method “by first appearance at the antenatal clinic.” The duration of pregnancy, and, accordingly, the date of birth in this case is determined by the following parameters - the size of the uterus and the level of human chorionic gonadotropin in the blood. When examining a woman in a gynecological chair, an obstetrician-gynecologist determines the size of the uterus with both hands. This method “works” most accurately in the early stages of pregnancy, up to about 12 weeks. The earliest period that can be determined by the size of the uterus is 5 weeks of pregnancy. By this time, the uterus is slightly enlarged, softens and becomes rounded. At later stages, the size of the uterus may vary slightly depending on the size of the fetus, the amount of amniotic fluid, and the structure of the woman’s pelvis.

A blood test for hCG (human chorionic gonadotropin) helps determine the gestational age and calculate the approximate date of birth in the early stages. It begins to be produced in the body of the expectant mother with the onset of pregnancy, and gradually, until about the 11th week of pregnancy, its amount increases and then decreases slightly. Determining the concentration of hCG in the blood at the beginning of pregnancy helps to accurately determine its duration. Having received the results of a blood test for hCG, it is worth paying attention that in laboratory tables, which determine the correspondence of the hormone level to the gestational age, the embryonic period is often indicated. That is, to determine the usual obstetric gestational age, 2 weeks should be added to the result obtained.

Method 4. Method for determining the due date about ultrasound

When performing an ultrasound in the early stages of pregnancy, measuring the size of the fertilized egg and embryo, the gestational age can be determined with great accuracy. At 4–5 weeks, an ultrasound examination reveals a small “black circle” in the uterus - this is the fertilized egg, in which the embryo will appear a little later. At about 6–7 weeks, the embryo appears as a small “stripe” and its heartbeat can be seen. The term calculated by measuring the CTE of the embryo is considered more accurate (CTE is the coccygeal-parietal size, that is, the maximum distance from the fetal head to its tailbone). After 12 weeks, the gestational age is determined by ultrasound by measuring the various sizes of the head and abdomen of the fetus, the length of its arms, legs, etc.

Until 9–10 weeks of pregnancy, the embryo grows proportionally, and its size in all women with the same gestational age will be approximately identical. In the future, these indicators will differ for expectant mothers of different nationalities, with different body weights, the weight of mom and dad at birth will also matter, and so on. That is, in later stages of pregnancy, normally developing children of the same “age” can have different sizes (fluctuations can be about 2 weeks and sometimes even more), and in such a situation, the gestational age cannot be reliably determined by ultrasound data.

Method 5. Method for determining the due dateabout the first movement of the fetus

Let us note right away that this method of determining PDR has recently been used less and less. It is based on the fact that women carrying their first child begin to feel its first movements on average at about 20 weeks of pregnancy, and those pregnant for the second or more times - a little earlier, at 18 weeks. That is why obstetrician-gynecologists recommend that the expectant mother remember the date of the first movement of the fetus and enter this data into the exchange card. To calculate the expected date of birth for women preparing to become a mother for the first time, 20 weeks must be added to the date of the first fetal movement, and for women expecting a second baby - 22 weeks.

However, this method of determining the date of the upcoming birth is often erroneous. What's the matter? The problem is that the time when a woman can feel the first movements of the fetus is very individual and depends on her sensitivity, body type, as well as employment and experience. So, some expectant mothers feel the first movements already at 15-16 weeks, and some only after 20. Slender women, as a rule, begin to feel them earlier than plump ones. Expectant mothers who lead an active lifestyle and work a lot usually feel fetal movements later than those who are less busy and have more opportunities to listen to their inner feelings. Pregnant women for the second or more times already know exactly how the baby’s movements are felt, therefore, as a rule, they recognize the baby’s movements earlier than “inexperienced” first-time women, who often mistake fetal movements for increased intestinal motility and gases.

All of the methods described above allow you to calculate the expected date of birth. However, we must remember that, of course, it is not absolutely accurate. Prematurity or miscarriage is common. The onset of premature labor can be triggered by abnormal development of the fetus, pathological processes in the body of the expectant mother, stressful situations, hereditary factors and many other reasons. Therefore, it is very important to realize that calculating the date of birth is a very conditional concept, regardless of the method used, and it is not possible to predict exactly when the baby will be born.

How is the expected due date calculated during IVF?

In the case of IVF (in vitro fertilization), fertilization of an egg with a sperm is carried out “in vitro” by an embryologist. Embryos develop in the laboratory for 3–5 days, after which they are transferred to the uterus. Doctors calculate the true gestational age following IVF from the date of ovarian puncture, that is, a procedure in which follicular fluid and the follicles contained in it are taken with a special needle for subsequent in vitro fertilization, and 2 weeks are added to determine the “usual” obstetric period. to the date of ovarian puncture.

If the transfer of the embryo into the uterus was preceded by its cryopreservation (that is, freezing in liquid nitrogen), to determine the exact gestational age, doctors add 5 days to the transfer date (this is the number of days of embryo development before freezing), and to determine the obstetric period, add 2 to the resulting true gestational age. weeks and calculate the due date.

The question of how to determine the due date often causes discussion and controversy among pregnant women. The difference between your own calculations, the deadlines that are set during an ultrasound examination and those that the doctor writes on your card is completely confusing. Specifically, in order to make life at least a little easier for pregnant women, we have developed a program that independently calculates the approximate date of birth. Now you don’t have to visit a doctor or bother yourself with mathematical calculations; in order to calculate the date of birth of your baby, you just need to enter the number when your last menstruation began in the required column of the calculator.

Naegele's formula is a two-step problem.

The program that allows you to calculate the date of birth is based on the Naegele formula, named after the German obstetrician who first proposed using this simple method of calculation. It is known that pregnancy lasts on average 40 weeks from the beginning of the last menstruation or 38 from the moment of conception. Nägele simplified the calculations by reducing them to a few simple arithmetic operations - remember the date of the onset of menstruation preceding pregnancy and subtract 3 months. You need to add 7 days to the resulting figure - this number is the very date of birth.

The question often arises: why should the date of birth be calculated based on the date of the last menstruation? This tradition, generally accepted in obstetrics, is justified, because not all women know exactly the day of ovulation, while the majority keep a menstrual calendar. It is also natural to be bewildered - after all, in the first, so-called “weeks of pregnancy,” conception has not even occurred yet. Yes, this is true, and this period refers to the period of pregnancy conditionally, for the convenience of obstetricians and gynecologists, according to standards. The fetus begins to exist when about 14 days of pregnancy are already behind. If the date when fertilization occurred is reliably known, you can calculate the date of birth yourself by adding 266 days or entrust this to our calculator.

Is deviation from the estimated date normal?

It is worth noting that the expected due date is nothing more than a guideline for you. In fact, about 17% of women give birth on day X, the remaining 83% a little earlier or later. No specialist can predict the onset of labor. Moreover, normal, term births, that is, births that occurred within physiological periods, are considered to be those that occurred from 38 to 42 weeks of pregnancy. Unpredictable miscarriage or miscarriage of pregnancy often occurs. The onset of premature labor can be triggered by abnormalities in fetal development, pathological processes in the maternal body, stressful situations, hereditary factors and many other reasons. Therefore, it is very important to understand that calculating the due date is a very conditional concept, regardless of the method used.

However, there is a certain pattern, taking into account which we can assume the development of the situation during a healthy pregnancy - the longer the monthly cycle, the longer the pregnancy lasts. Before you determine your due date, taking into account your individual characteristics, remember the duration of your menstrual cycle - from the first day of some periods to the first day of others. If the cycle is longer than the standard 28 days, the pregnancy will probably last more than 40 weeks, and vice versa. Keep in mind that we are talking about postponing the estimated date of birth by no more than 5 days.

The calculator will help you calculate the date of birth based on your period as accurately as possible, but you should remember that the data obtained during a medical examination is crucial, as it is more reliable. The reason for this approach is that menstruation can easily be confused with bleeding that began after conception and stopped spontaneously. Also, during an examination in the third trimester or an ultrasound of the uterus, the doctor can observe the degree of maturity of the placenta, the position of the fetal head in relation to the entrance to the pelvis, the opening of the cervix, signs of full-term fetus and many other important data. Based on all these parameters, one can judge the readiness of the fetus and uterus for labor and the likelihood of its imminent onset. In addition, focusing on the size and proportions of the fetus during ultrasound examination, the doctor determines the age of the fetus in accordance with.

Estimated due date(PDR) is the day after the end of the 40th week of pregnancy. A mature, healthy baby can be born between 38 and 42 weeks (gestational age is the time that has passed since the fertilization of the egg). Thus, the PDR is the date on which it is customary to focus.

It is important for a gynecologist observing an expectant mother to know exactly what stage of pregnancy the woman is in in order to understand whether the pregnancy is proceeding correctly and the child is developing, whether its size and development of organs correspond to this period (whether there is a delay in fetal development), and also for establishing expected date of birth. The PPD must be calculated in order to determine in what week the baby should be born, to determine whether the pregnancy is post-term (lasting more than 42 weeks), to prevent the danger of possible premature birth (up to 37 weeks of pregnancy), because this can negatively affect the health of the child .

Estimated due date is also important when it becomes necessary to hospitalize a woman in a maternity hospital before she goes into labor. This happens when it is necessary to decide on the tactics of labor management - to carry out an independent birth or perform a planned cesarean section (it is indicated, for example, in case of placenta previa - a condition when the placenta is located in the lower part of the uterus and completely or partially covers the internal os - or in transverse fetal position).

How to find out your due date: menstruation

In a antenatal clinic or in a maternity hospital, the gynecologist first of all asks the expectant mother when was her last menstruation before pregnancy. Gynecologist to determine the duration of pregnancy and dates of expected birth you need to know the first day of your last menstrual period. (It is from this day that the menstrual cycle is counted and its duration is calculated).

To find out the due date, you can add 280 days to the date of the first day of the last menstruation (a normal pregnancy lasts about 280 days). Also expected date of birth can be found out in an easier way - using Naegele's formula. In order to calculate the expected date of birth from it, it is necessary to subtract 3 months from the first day of the last menstruation and add 7 days. For example, a woman’s last menstruation began on June 13th. Subtract 3 months - it turns out March 13th. Now we add 7 days to March 13th. It turns out that March 20 is the expected date of birth.

Calculated by date of last menstruation expected date of birth is considered the obstetric stage of pregnancy. With an irregular menstrual cycle, it is very difficult to determine the date of ovulation and using this method to determine the expected date of birth is considered incorrect.

Calculate your due date based on menstruation using our Due Date Calculator

How to find out your due date: conception and ovulation

The most suitable moment for conception is the time of ovulation, that is, the time the egg is released from the ovary. With a cycle duration of 28 days, ovulation usually occurs in the middle of the cycle - on the 14th day. At this time, the probability of getting pregnant is maximum.

Taking into account the lifespan of a sperm (it reaches 3–5 days), possible conception can occur as early as the 9th day from the start of menstruation (if sexual intercourse occurs before ovulation, the sperm “survive” until fertilization). The egg has a lifespan of 1 day. If the menstrual cycle is shorter (21–24 days), then ovulation occurs earlier - on the 10–12th day; if the cycle is long (32–35 days), then ovulation usually occurs on the 16–18th day from the start of menstruation. For example, menstruation began on May 10, the cycle is 28 days. We expect ovulation on May 24; the period from May 19 to May 24 will be suitable for conception; pregnancy is also possible on May 25, but from May 26 it is unlikely.

So, if the date of conception or the day of ovulation is known, then the gestational age can be determined more accurately. You just need to remember that then we will be talking about the true (embryological - calculated by the date of ovulation) pregnancy period, and the real duration of pregnancy is 266 days - 38 weeks, i.e. it is necessary to add 266 days to the date of ovulation (conception), this and will expected date of birth.

With a normal (28 days) menstrual cycle, the difference in expected date of birth when calculating by menstruation and conception there should not be.

How to find out your due date: movement

Find out the due date it is possible based on the date of the first movement of the fetus (it is more correct to talk about the moment when the expectant mother first felt movement, since the baby begins to move already from 8 weeks of pregnancy).

Primiparous women most often feel fetal movement at 18–20 weeks of pregnancy, and multiparous women - from 16 weeks. To calculate the expected date of birth for a primiparous woman, 20–22 weeks are added to the date of the first fetal movement; for a multiparous woman, 24 weeks are added. This method can most often be considered more as an auxiliary method, because fetal movement is an extremely subjective sensation.

A first-time mother may not notice it, confusing it with intestinal peristalsis (contractions), or, conversely, mistaking the sensations in the intestines for the movements of the baby.

Multiparous women who already imagine the sensations of fetal movement may feel it a little earlier. Some mothers may not feel fetal movements until 21–22 weeks. This is due to both the activity of the baby and its location in the uterus, as well as the sensitivity of the walls of the uterus.

To speed up the calculation of gestational age based on menstruation and the first movement of the fetus, there are special obstetric calendars and rulers.

How to find out your due date: examination by a gynecologist

The sooner a woman contacts an antenatal clinic, the more accurately the pregnancy period will be determined and the more accurately the pregnancy will be determined. expected date of birth. It is believed that the error will be minimal if a woman consults a doctor in the first 12 weeks of pregnancy. An increase in the size of the uterus, which the doctor can already feel, during a vaginal examination occurs after 4 weeks of pregnancy. Before this period, it may be difficult to accurately determine the gestational age using manual examination, especially if it is the first.

Determine the gestational age and expected date of birth it is impossible to accurately measure up to the day during inspection, since this method is subjective. In pregnant women, the uterus takes on a spherical shape (in non-pregnant healthy women, the uterus is pear-shaped) and increases in size, becoming soft (the non-pregnant uterus is hard to the touch). There are also certain criteria that the doctor follows when making the necessary measurements. For example, at 4–5 weeks of pregnancy the size of the uterus reaches the size of a chicken egg, and at the end of 12 weeks it reaches the size of a newborn’s head.

A doctor observing a pregnant woman in later stages determines the duration of pregnancy, and therefore assumes due date, by determining the height of the uterine fundus.

From 14–16 weeks of pregnancy, the gynecologist can determine the gestational age and approximate due date using an ordinary examination (not on a gynecological chair) - by palpating the abdomen, the fundus of the uterus (the uppermost part of the uterus) is determined, which at this time is located in the middle of the distance between the pubis and the navel. By touch, the doctor will determine the height of the uterine fundus, on the basis of which it will be possible to judge the gestational age and calculate the expected date of birth. This method is not reliable enough, since the doctor is based on subjective data. In addition, diseases such as uterine fibroids (a benign tumor of the muscle tissue of the uterus) can increase the size of the uterus.

Find out the due date can be done using ultrasound (ultrasound). To determine the date of expected birth, ultrasound data obtained from the 4th to 12th week of pregnancy are considered the most informative.

During this period, determining the gestational age is based on measuring the fetal egg and its average internal diameter. Having undergone an ultrasound in the early stages, you can find out the gestational age with an accuracy of literally one day and, in accordance with this, calculate the approximate date of conception and expected date of birth.

Gestation period in I trimester can be determined quite accurately by the CTE (coccygeal-parietal size of the embryo). Each stage of pregnancy corresponds to a certain CTE. In the second and third trimesters, the gestational age is determined based on the determination of such parameters as BDP - biparietal head size (transverse size of the head), fetal head circumference, average diameter of the fetal chest and abdomen, fetal abdominal circumference, femur length. The most reliable information is considered to be obtained by measuring the baby's head circumference and BPD.

Ultrasound result obtained in I trimester(first 12 weeks of pregnancy) allows you to calculate expected date of birth with an accuracy of 1–3 days, in the second trimester (from 13 to 28 weeks) the error increases to 7 days, and after 28 weeks (third trimester) it is very difficult to judge the gestational age based on the ultrasound dimensions of the baby. The increase in ultrasound error in calculating the expected date of birth is due to the fact that the gestational age in this study is judged by the size of the child. Exactly at I trimester The size of the fetus corresponds as closely as possible to the gestational age. And the main differences in weight and height occur in children in the last trimester of pregnancy (birth weight can range from 2500 to 4500 g), which depends on the influence of hereditary factors, complications of pregnancy, for example, the development of fetal growth retardation, etc.

When establishing the duration of pregnancy, the doctor relies on a large number of symptoms and signs and takes into account their combination. The earlier a woman consulted, the more carefully she attended, the more opportunities the doctor has to accurately determine expected date of birth. But even in this case, inaccuracies are possible.

With all the variety of methods for determining the expected date of birth, there is no one “absolutely accurate” method. Therefore, we can say that a more or less accurate determination of the date of the upcoming birth is possible if all the data obtained are not contradictory, but complement and reinforce each other.

Estimated due date

Contrary to the hopes of many expectant mothers, especially those expecting their first child, it is almost impossible to determine the exact date of birth in each specific case. This date is assumed to be accurate to within a few weeks (+?/ – 2 weeks from the calculated period of 40 weeks). There are many reasons for this.

Firstly, even if a woman knows the exact date of sexual intercourse, which became the beginning of pregnancy, this does not mean at all that she knows the exact date of fertilization. After all, sperm can live in a woman’s body for several days, maintaining their fertilizing ability.

Secondly, when the date of pregnancy is calculated based on the timing of ovulation, it must be taken into account that ovulation can occur between the 9th and 16th day of the menstrual cycle, depending on its duration. If a woman’s menstrual cycle is 28 days (counting from the first day of menstruation to the first day of the next), then ovulation occurs on the 14th day of the cycle, and if it is shorter (for example, 20 days), therefore, ovulation will occur earlier - in the middle of the cycle by 10 th day. Also, the menstrual cycle should be regular.

Finally, the duration of pregnancy is not always exactly 40 weeks - the pregnancy is considered full-term by the 37th week, after which birth can occur at any time. For example, a multiple pregnancy almost always ends in birth 1–2 weeks earlier than a singleton pregnancy. Sometimes incorrect positioning of the fetus and polyhydramnios interfere with accurate orientation.

Also factors influencing the duration of pregnancy and the onset of childbirth are the woman’s age, the number of previous pregnancies, births, abortions, placental function, the presence of chronic diseases and many other circumstances.

It has been established that the actual date of birth in 95% of cases does not coincide with the date that was originally set. Thus, only 5?% of women give birth on the appointed day.

However, it is possible to determine the approximate date of birth, which doctors do with success.