All about how doctors determine the duration of pregnancy and something else. Determining the gestational age: possible options

Pregnancy is a long-awaited and desired event for many women. And now you will be interested to know everything about your situation: how the pregnancy develops week by week, what is happening in the body. And with the help of a pregnancy calendar you can do this very quickly and easily.

The pregnancy calendar is a convenient and useful service for expectant parents, moms and dads, which will tell you in great detail about pregnancy week by week. He can be your companion throughout your pregnancy right up to the birth itself.

Pregnancy is divided into 3 trimesters:

1. First trimester - 1-13 weeks after conception
2. Second trimester - 14-26 weeks
3. Third trimester - 27-40 weeks

How does the fetus develop during each trimester? Our pregnancy calendar will give you the answer.

Why do you need a pregnancy calendar?

The pregnancy calendar will tell expectant mothers about how their baby changes and grows at this or that stage, how its organs develop, and how the baby gains weight. Our calendar for pregnant women will tell you what to do and what to abstain from at each stage of pregnancy, which doctors you need to visit, how to eat and what lifestyle to lead so that your baby is born healthy.

Also, our online pregnancy calendar will help you find out in what week, using an ultrasound, you can determine if you are having a girl or a boy.

This is exactly the weekly pregnancy calendar that gynecologists use when determining the age and development of the fetus. But there is also the age of the fetus, which differs from the menstrual period of pregnancy by 2 weeks.

In addition, this online pregnancy calendar gives expectant mothers the opportunity to communicate and exchange their feelings and impressions with friends in an interesting position every week of pregnancy. Leave your comments and you will find out who has the same feelings and what they could mean.

But you need to know that every pregnant woman’s body is different, and our calendar does not take into account individual characteristics menstrual cycle, so the calendar contains information that is common to everyone. All dates are approximate, as the length of the menstrual cycle is different for all women and can vary, as a rule, from 24 to 36 days. In addition, you need to take into account that the cycle may be irregular.

Reviews

Galina Chalaya
I approached the moment of conception very consciously and, of course, I take pregnancy responsibly. It is very important for me to know what happens to the baby at each stage of his development. After all, from the moment of conception he is my child, whom I must take care of. Therefore, I am happy to definitely look at the pregnancy calendar and read how my little son is doing in my tummy.

Natalia Semerichko
For me, the most important thing was that while reading about my week of pregnancy, I could chat on the forum and discuss my feelings with other expectant mothers who are at the same stage.

Maria Krylova
This calendar helped me learn a lot about my future baby. useful information. During this period, I was most interested in how it was in my tummy. After all, this pregnancy was my first.

Very convenient and useful service. Thank you very much!

Send your reviews about the Pregnancy Calendar to editorial@site
Why do pregnant women and doctors need to know what stage of pregnancy it is? Firstly, to determine the due date, secondly, to adequately monitor the development of the baby, correcting possible developmental delays in a timely manner, and thirdly, to determine the date of maternity leave. I would like to make a reservation right away that there is a difference between obstetric and true pregnancy periods. Obstetricians begin to count the gestational age from the 1st day of the last menstruation. This is quite justified, because from this moment the egg begins to mature, which will later be fertilized by a sperm, a zygote is formed and implanted in the uterus, a fertilized egg with an embryo and then a fetus will begin to develop (after 12 weeks of pregnancy). The duration of pregnancy from the first day of the last menstruation until childbirth is about 10 lunar months or 280 days or 40 weeks. However, each fruit has its own term intrauterine development
The true pregnancy period lags behind the obstetric date by two weeks - it is counted from the day of ovulation and conception. Thus, to determine the obstetric gestational age, two weeks must be added to the true one.

How to find out the gestational age by ovulation and date of conception

Ovulation is the very period of the menstrual cycle when conception of a child can occur. During ovulation from a woman's ovary fallopian tube a mature egg is released and “waits” for sperm there. Unprotected sexual intercourse at such a time is more or less healthy woman and men will most likely lead to pregnancy. The date of ovulation is used to determine the duration of pregnancy.
A woman ovulates around the middle of her menstrual cycle (but not every month). If your menstrual cycle is 28 days, then ovulation will occur somewhere on the 14th day, with a 35-day menstrual cycle– on the 17-18th day of the cycle. The exact duration of pregnancy should be counted starting from the day of ovulation.
Ovulation can also be determined at home, using special tests sold in almost any pharmacy, or by regularly measuring basal temperature (temperature in the rectum). Throughout the first half of the cycle it will remain at approximately the same level - below 37 degrees. The day before ovulation it will decrease slightly. And on the day of ovulation and on all subsequent days you will maintain a level of 37-37.2 degrees. Thus, you can calculate the duration of pregnancy (), if it began in the menstrual cycle when you determined your ovulation.
There are women who can determine their ovulation without any tests or temperature measurements, simply by subjective sensations - pain in the lower abdomen, increased libido, increased amount of vaginal discharge. It is easy for such sensitive women to determine the duration of pregnancy on their own.
The most accurate way to determine the gestational age by the date of ovulation is an ultrasound. This is the only way to accurately see ovulation. But it’s problematic to go for an ultrasound every day for a week, or even longer. And financially, such “pleasure” will not be available to every woman. Trying to determine your ovulation only so that you can later accurately calculate the duration of your pregnancy is inappropriate. There are more simple ways calculating the gestational age already, in fact, after the onset of an interesting situation.

The number of days (weeks) at the time of examination of the pregnant woman is counted from the first date of the last menstruation. To determine the day of birth, add 280 days (10 lunar months) to the first day of the last menstruation or use the Naegele formula: subtract 3 months from the start date of the last menstruation and add 7 days. This method cannot be used in women with irregular menstrual cycles.

Determining the gestational age by gynecological examination.

If you come for an examination to a gynecologist in the first weeks of pregnancy (at 3-4 weeks), then it will not be difficult for the doctor to accurately determine the gestational age. IN in this case based on the size of the uterus. For example, at 4 weeks of pregnancy, the size of the uterus can be compared with chicken egg, at 8 weeks - with a goose egg. An experienced gynecologist is able to determine the gestational age through a vaginal examination with an accuracy of one day. It will be difficult to accurately determine the gestational age beyond 8-12 weeks simply based on the size of the uterus. Since starting from the second trimester of pregnancy, the size of the uterus may differ in women at the same stage of pregnancy.

Determination of gestational age by ultrasound.

Of course, here, as with the previous method, much depends on the qualifications of the doctor who interprets the results. Ultrasound data obtained before the 12th week of pregnancy are considered the most correct for determining the date of expected birth. At this stage, the determination of the gestational age is based on the measurement ovum, its average internal diameter.
In the second and third trimesters, the gestational age is determined based on the determination of such parameters as fetal head circumference, average diameter chest and fetal tummy, fetal abdominal circumference. The most reliable information is considered to be obtained by measuring the circumference of the baby's head.
However, it is generally believed that in later stages of pregnancy the error in determining the due date using ultrasound increases. This is understandable: after all, each child develops individually, and at the end of pregnancy, the size of the fetus, which the doctor focuses on in his calculations, can vary significantly depending on the characteristics of a particular child.
With all the variety of methods for determining the date of the upcoming birth, there is no one “absolutely accurate” method, as we have already said. 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.
Although even in this case, the date of birth may shift by one or two weeks in one direction or another due to the fact that term birth (that is, birth at term) can occur in the period from 38 to 42 weeks of pregnancy.

Determining the gestational age by the first movement.

Primipara women begin to feel the first movements of the baby at 20 weeks of pregnancy. Multiparous women a little earlier - at 18 weeks. Gynecologists recommend that a woman remember the date of her first movement and be sure to include it in the pregnant woman’s dispensary card. This is of great importance when determining the due date of pregnancy and childbirth. For example, in order to determine the date of birth, you need to add 20 weeks (or 4.5 months) to the date of the first movement; for multiparous women, you need to add 18 weeks or 5 months.
But this method of determining the gestational age is not always correct. There are women who, even in their first pregnancy, feel the baby’s movements much earlier due date at 20 weeks, at 17 weeks, or even earlier. Such early movements are especially often observed in skinny women. There are women who feel the first movements 2 weeks later than expected.
Doctors have their own opinion about such early movements and setting the gestational age based on them. Most experts believe that women before the due date do not feel the baby’s movements at all, but the “work” of the intestines. After all, as you know, most pregnant women suffer from increased gas formation...

Determination of gestational age by measuring the length of the uterus and fetus.

You can calculate the gestational age in a more complex way. Only a gynecologist can make such a calculation. You are unlikely to succeed on your own. So, in order to measure the length of the uterus, a woman lies down on the couch and straightens her legs. It is necessary to empty it first bladder, otherwise errors in determination are possible the right time pregnancy. The length of the uterus is measured using a centimeter tape or a pelvis gauge. Usually the length of the uterus is equal to the number of weeks. For example, the length of the uterus is 36 cm, which means the gestational age is also 36 weeks.

Pregnancy calculators

The calculator calculates the duration of your pregnancy based on your last menstrual period. The gestational age is obtained in “obstetric” weeks.

As a rule, every pregnant woman has her own calendar, where she enters all the necessary data, circles important dates, and makes notes. It is usually used to calculate the gestational age.

Considering the nine-month duration of this period, calculations on paper seem to be a very routine task. But modern women live in excellent times - they are not at all obliged to keep such a calendar and do tedious arithmetic, unless, of course, they are so sentimental that they decided to keep their weekly notes as a memory of the wonderful time of pregnancy. You can safely entrust the worries about calculating your pregnancy period to the program. After all, for those who prefer to spend their free hours on activities that are much more useful for the future baby and his mother, there are numerous virtual services like this (we hint at our calculator).

What is needed to calculate the gestational age?

In order to calculate the gestational age right now, you only need to remember the date when your last period began and enter it in the appropriate fields of the form. This number is the starting point of your pregnancy. We are talking about the so-called “obstetric weeks” - all over the world it is customary to count pregnancy this way, although fertilization occurs only in the middle of the cycle. This measure is necessary for the convenience of doctors, but often causes surprise and misunderstanding among patients.

It is worth noting that during an ultrasound examination of the fetus, you will be faced with the fact that the gestational age known to you can be calculated differently - based on the weeks of the fetus’s life, that is, from the day of conception. You may even find a note on the ultrasound examination results sheet that will indicate both dates. In order not to be embarrassed by such contradictions, feel free to ask your doctors what exact stage of pregnancy you are talking about, real or obstetric?

It is very important to emphasize that even if you know exactly the date of conception of the baby, in order to calculate the gestational age using a calculator, you need to use the date of the start of the last menstruation. If you find it difficult to remember, count back 2 weeks - with a standard 28-day cycle, ovulation most often occurs on the 14th day.

I don't remember when I had my period. What to do?

Sometimes it happens that a woman does not know when she had her last period, for example, she does not remember, does not monitor the regularity of her cycle, or has just stopped taking birth control medications. If you have no idea what your gestational age is, they can calculate it using. The most reliable data is obtained in the early stages (up to 12 weeks), when the rate of development of the fertilized egg is still very high and changes are noticeable literally every day. The size of the fertilized egg alone, without taking into account the proportions of the fetus, will tell the doctor a lot. For more later There may be errors of up to 2 weeks.

Another very informative method that allows you to calculate the gestational age is biochemical - testing a woman’s blood for the content of hCG - human chorionic gonadotropin. This hormone is produced by the fertilized egg and is present in the body only during pregnancy (by the way, the well-known instant pregnancy test is based on its determination in urine). Contents and healthy pregnancy clearly corresponds to deadlines. It is worth noting that this is far from a routine method, which requires a lot of time and money, and is used mainly for medical reasons.

It is impossible not to mention that finding out the gestational age, calculating and guessing probable age fetus is within the competence of the obstetrician when performing vaginal examination in the early stages. The main object of study in this case will be the uterus and palpation (manual) determination of its size. Of course, we are not talking about absolute accuracy, but the data obtained is quite sufficient for successful monitoring of the health of the expectant mother and fetus.

Questions for the article

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Having learned about pregnancy, any woman will want to calculate its approximate duration in order to schedule a visit to the doctor, registration with antenatal clinic and, of course, start preparing for a significant event in your life - childbirth.

It is not difficult to calculate it, you just need to understand how to do it. It’s easy to find out if you remember the start date of the last cycle, that is, the last menstruation, and count the weeks from it. This period is called obstetric. On the Internet you can now even find special services that calculate the duration of pregnancy in accordance with the start date of the last cycle and its average duration.

But if the cycle is unstable and changes frequently, such a method can hardly be called reliable, so a logical question arises about how to find out exact date pregnancy.

You can find out the period quite accurately by using the new generation, which will especially help in the early stages, at the very beginning of pregnancy. Such tests determine the concentration of beta-hCG, a hormone that begins to be produced, and give an approximate result.

An obstetrician-gynecologist can also tell you how to find out the duration of your pregnancy. As a rule, doctors use two methods: a blood test for a special indicator, beta-hCG, and ultrasound.

A blood test, especially if done closer to 10-12 weeks, may give an insufficiently accurate result, since at these times the normal limits are already too wide to accurately determine the period. But ultrasound can give results more accurate even than the obstetric period. Measuring the size of the fetus and comparing them with a table of norms helps to establish the period very accurately, however, it is called embryonic and is often slightly behind the obstetric one. At the same time, the doctor can tell you how to find out the due date; it is not difficult to calculate it.

There are several other ways to find out your gestational age. For example, you can learn to measure by asking your doctor to show you how to do it. It will be difficult at first, but as the uterus rises, it will become easier to take measurements. Normally, this value is equal to a week of pregnancy.

There is a method that even doctors focus on - the time when the expectant mother begins to feel the fetus moving. This usually happens in Some pregnant women even believe in the superstition that by counting exactly 20 weeks from the moment of the first movements, you can find out the date of birth.

The closer the end of pregnancy is, the easier it is to determine its exact duration using ultrasound. While in the early stages the equipment could have interfered or was not good enough, now that the baby is already big, it is easier to measure it.

You can ask different doctors how to find out the duration of pregnancy, but only the woman herself can accurately answer this question, focusing on her own feelings and well-being.

It should be remembered that in most cases, babies are not born exactly on time, but earlier or later by several days, or even two weeks. This is considered normal, so there is no need to worry. But you should definitely take into account that the due date given by the doctor is only an approximate date, so it is better to prepare for childbirth in advance.

Determining pregnancy in the early stages is important for a woman. Thus, almost 50% of embryos die in the first two to three weeks from the moment of conception. This occurs due to the fact that the embryo is defenseless against infection, which may be in the mother’s body due to bad habits and other negative factors. Taking medications, smoking, prolonged exposure to the sun and drinking alcohol are the most common reasons death of the embryo in the first months of pregnancy. Many women may not be aware of their situation and continue to lead a lifestyle that is fatal to the development of the embryo.

Determining pregnancy in the early stages is also necessary for those women who are planning to have an abortion. Since late abortion can lead to infertility in the future and serious complications. Medical abortions done during the first four to six weeks of pregnancy, and vacuum aspiration or mini-abortion within 20 days after a missed period and confirmation of pregnancy. Classic abortion (curettage) is performed before the 12th week of pregnancy. But the optimal period for abortion and preserving a woman’s health is considered to be 6-8 weeks.

The onset of pregnancy is determined by various signs, both changes in the appearance and behavior of the pregnant woman. Frequent mood changes, vulnerability, change taste preferences, increased sensitivity, nausea (especially in the morning), swelling of the extremities, delayed menstruation and swelling of the mammary glands may indicate pregnancy in early.

Methods for determining gestational age

Methods for determining the duration of pregnancy allow you to determine how much time is left before birth and how it is developing. unborn child. Let's look at the most popular methods for determining the duration of pregnancy.

• According to menstruation and the results of examination by a gynecologist. In early pregnancy, the uterus enlarges to the size of a chicken egg.
• According to ultrasound data, the accuracy of determining pregnancy using ultrasound is quite high in the first trimester.
• By ovulation - the gestational age can be determined by the date of expected conception, adding 14 days to it. Using this method, the date of birth is also determined. To do this, three months and seven days are counted from the date of ovulation.
• By bimanual examination - this method allows you to determine the gestational age by palpating the position of the uterus. In the first trimester, the uterus is located in the pelvic area, and starting from the second trimester, it can be felt above the womb.

Pregnancy test

A test to determine the gestational age is modern method find out the time before going to the gynecologist. The most popular test among expectant mothers to determine the duration of pregnancy is Clearblue. The test is easy to use and gives results with an accuracy of up to 99%.

Clearblue with gestational age detection

Clearblue pregnancy test is a digital test that shows double results on a special Smart Dual Sensor display. So, with the help of a test you can not only confirm pregnancy, but also find out its duration. Let's look at the benefits of the Clearblue test.

• Now there is no need to look at the stripes on the express test, since the digital display will show reliable result, which will last for 24 hours.
• Clearblue is the only test of its kind that provides information about the gestational age, that is, the amount of time that has passed since conception.
• The test gives a 99% accurate result from the first day of the delay.
• The test is very simple and easy to use.
• Clearblue has received approval from obstetricians and gynecologists around the world.

Determining the gestational age of a child

Determining the gestational age of a child is carried out using several methods. Some methods are based on the date of the last menstruation and the duration of the delay, others on the signs of pregnancy that appear in a woman, and others make it possible to find out the gestational age using a digital test. Another way to determine your baby's gestational age is to undergo a gynecological examination or ultrasound examination. Each woman decides independently which method to use. On average, after conception, it takes about seven days for the sperm to fertilize the egg. That is why many women focus on the period of ovulation. Please note that it is recommended to plan your pregnancy according to the timing of ovulation.

Determination of gestational age by ultrasound

Determining the gestational age by ultrasound is one of the most reliable methods. The use of ultrasound in the first weeks of delayed menstruation makes it possible to accurately diagnose the timing of pregnancy. An ultrasound is performed not only to determine the timing of pregnancy, but also to monitor the course of pregnancy and the development of the baby. Many gynecologists claim that the optimal period for reliable diagnosis of pregnancy is a period of up to 6 weeks. Diagnosing the gestational age by ultrasound in a later period will be difficult.

Ultrasound results in the first weeks after conception are based on the length of the fetus. The gynecologist measures the length of the fetus and compares the data obtained with the table values. This allows you to accurately determine the duration of pregnancy and monitor its progress. Throughout pregnancy, a woman should do control ultrasounds so that the gynecologist can monitor the development of the child and, if necessary, prevent the development of pathologies.

Determination of gestational age by week

Determining the gestational age by week is the task of the gynecologist. Knowing the exact duration of pregnancy, which is calculated in weeks, the gynecologist monitors the development of the child and the entire period of pregnancy. In addition, depending on the period, the doctor prescribes certain tests and studies that will help prevent the development of pathologies and complications in the child.

Weeks of pregnancy are obstetric (which are monitored) and embryonic. The obstetric period is 40 weeks, and the embryonic period is 38 weeks. To determine the exact period, the gynecologist observes the symptoms of pregnancy and the development of the embryo.

Determining the gestational age by menstruation

Determining the gestational age by menstruation is most often used, since this method is quite simple and effective. When examined by a gynecologist and determining the gestational age, the doctor learns about the date of the last menstruation and the duration of the cycle. These data make it possible to determine the gestational age based on menstruation. Gynecologists use the method of counting pregnancy from the first day of the last menstruation. Since it is almost impossible to establish the exact date of conception, and menstruation is the only guideline.

When determining the gestational age, gynecologists use a calculation formula based on the menstrual cycle of 28 days. This suggests that ovulation occurred on the 14th day from the start of menstruation. But this formula is not always accurate, since not all women have a regular menstrual cycle. Therefore, the determination of the period has an error. Gynecologists distinguish two stages of pregnancy, the first is obstetric (from the first to last day menstruation), and the second is embryonic (from the date of fertilization and ovulation).

Gestational age determination table

The table for determining the gestational age allows you to visually look at the expected date of birth and gestational age. The table is based on the results of tests and gynecological examinations. There are several criteria that serve as the starting material in the pregnancy determination table: the size of the fetus, the date of the last menstruation and diagnostic results.

We offer you a table for determining the gestational age based on the results of an ultrasound examination, that is, based on the size and weight of the fetus. The size and weight of the embryo in the first trimester are not taken into account in the table, as they are too small. Please note that the gestational age chart uses obstetric weeks of pregnancy.

Determining the exact duration of pregnancy

Determining the exact duration of pregnancy can be done using several methods. Each of them has an error, let's look at the most popular ones.

• Symptomatic - the duration of pregnancy is determined by certain symptoms. Thus, breast enlargement, lack of menstruation and increased sensitivity indicate early pregnancy. True, this method is very controversial, since in some cases the symptoms described above may indicate complications in the female body, and not pregnancy. That is, accurate this method is 50%.
• Ultrasound examination is a popular method for determining the gestational age. The accuracy of ultrasound results in determining the period is 100%.
• Digital tests are a modern method for determining the duration of pregnancy. The test accuracy is 99%.
• Gynecological examination is the most accurate method of determining the period. Using examination and test results, the gynecologist determines the gestational age. The accuracy of this method is 100%

Calendar for determining the duration of pregnancy

The calendar for determining the gestational age is based on Naegele's formula. Nine months and seven days of pregnancy are added to the date of the last menstrual period (its beginning) and subtracted three months. It is necessary to add another seven days to the received date, the result obtained is the preliminary date of birth. According to this formula, there is a special calendar.

If you don't trust calendar method, then you can check its effectiveness. Calculate the date of birth according to the calendar and compare it with the one that the gynecologist says after the examination. Please note that fetal movement is of great importance when determining the duration of pregnancy. It is with the help of the date of movement that you can calculate the exact date of birth. At the same time, for women who give birth for the first time, 22 weeks are added to the date of movement, and for those who give birth again, 20 weeks.

Determination of gestational age using hCG

Determining the gestational age using hCG is one of the most accurate methods. HCG or human chorionic gonadotropin is a protein hormone that is produced by the membranes of the embryo throughout pregnancy. It is hCG that blocks the processes in the female body that are responsible for the menstrual cycle and enhances the production of hormones that are responsible for maintaining pregnancy. HCG increases during conception and is one of the reliable signs the onset of pregnancy. HCG levels rise from the first week of pregnancy, that is, within 14 days after conception. This figure doubles every day, starting from the 3rd week of pregnancy and up to the 12th week. From 12 to 22 weeks the hormone level does not increase, but from 22 weeks it begins to rise again.

The rate at which hCG increases in the blood makes it possible to determine abnormalities in the development of pregnancy. So, when frozen or ectopic pregnancy, HCG is below normal. A sharp increase in this indicator indicates multiple pregnancy or about chromosomal diseases. Therefore, the gynecologist, as well as the pregnant woman herself, should monitor the dynamics of hCG concentration in the blood during pregnancy. Let's look at the norms for hCG levels and the effect of this hormone on determining the duration of pregnancy.

Please note that the values ​​​​indicated in the table are not a standard. So, depending on the characteristics of the woman’s body and the course of pregnancy, the hCG norms when determining the duration of pregnancy.

Determination of gestational age by conception

Determining the gestational age by conception involves calculating the period by week. On average, pregnancy lasts 280 days or 40 weeks. Obstetricians determine the gestational age based on menstruation and this is called obstetric weeks pregnancy. But determining the gestational age at conception is called the embryonic period, and it is based on the ovulation period. Every woman conceives in different period ovulation, therefore, when determining the due date by conception, it is recommended to add 38 weeks to the date of the last menstruation.

But do not forget that obstetricians keep track of their gestational age, which differs from the embryonic period (gestational age at conception). And all tests will have to be taken based on the obstetric stage of pregnancy.

Determining gestational age by ovulation

Determining the gestational age by ovulation is a simple and effective method. Ovulation is the period of menstruation during which pregnancy can occur, as a mature egg leaves the ovary and is ready for fertilization. On average, ovulation occurs on day 14 with a normal menstrual cycle of 28 days, and in women with a long cycle, ovulation occurs between days 15 and 18. To accurately determine the period of ovulation, you can buy a special test or measure your basal temperature. But some women can determine ovulation by certain symptoms (pain in the lower abdomen, increased vaginal discharge, increased sexual desire).

But the most accurate way to determine the duration of pregnancy by ovulation is ultrasound. Ultrasound allows you to accurately determine ovulation. True, regular ultrasound is expensive, so other simpler methods are used to determine the timing of pregnancy.

Determination of gestational age using KTR

Determining the gestational age using CTE is possible only with the help of an ultrasound examination. At the beginning of pregnancy, a woman undergoes an ultrasound, which measures the fertilized egg. CTE is the coccygeal-parietal size of the embryo, which can be measured using ultrasound imaging. KTE is the maximum distance from the tailbone to the crown. The CTE indicator is used to determine the exact duration of pregnancy during the first trimester. Let's look at these indicators:

If the exact duration of pregnancy needs to be determined in the second or third trimester, then other indicators are used instead of CTE. The biparietal size or BPD, that is, the size between the temporal bones, is important. Another indicator for determining the exact duration of pregnancy is the circumference of the pregnant woman’s abdomen, the length of the thigh or femur. Let's look at the values ​​of these indicators and the gestational age. Fetometric parameters in the second and third trimesters of pregnancy:

All of the above indicators are used by modern ultrasound machines to determine the duration of pregnancy. But, do not forget that the indicators may differ from the real ones. Thus, when measuring CTE, the error may be within a week of pregnancy, and when obtaining BPR, the error is up to 11 days.

Formula for determining gestational age

The formula for determining the gestational age is used by many women. Let's look at the most accurate and popular formulas.

• Nägele's formula for determining the date of birth based on the last menstrual period
• To calculate, you need to know the date of your last menstruation and subtract three months and seven days from it.
• Jordania formula

The formula itself looks like: X = L + C, the X value is the gestational age in weeks, L is the length of the embryo, and C is the size of the head, measured by the pelvis. Let's look at this formula in practice. L – 18 cm, C – 12 cm, that is X = 18 + 12 = 30 weeks of pregnancy. But according to research, there is an error of 2 weeks in this formula.

• Skulsky's formula

This formula allows you to accurately determine the duration of pregnancy in the last trimester. So, the formula: X = ((Lx2)-5)/5, where X is the obstetric gestational age, L is the length of the embryo, 2 is the coefficient that allows you to determine the length of the fetus, 5 in the numerator is the coefficient of the thickness of the uterine walls, in the denominator – indicator from the Haase formula.

• Haas formula

A formula that was developed by an obstetrician-gynecologist to determine the intrauterine age of the embryo during the first 20 weeks of pregnancy. In the first 20 weeks, the length of the embryo in cm is equal to the square of the months of pregnancy, in the last 20 weeks - the number of months of pregnancy multiplied by 5.

Accuracy of determining gestational age

The accuracy of determining the gestational age depends on the method used and the characteristics of the course of pregnancy. To determine the exact date to the expectant mother you will have to undergo many tests. The most accurate method is considered to be ultrasound examination, the use of digital tests and gynecological examination.

Determining the gestational age has important for every woman. Knowing the age of the embryo, the gynecologist can monitor its development, the course of pregnancy and prevent various pathologies and complications. In addition, the exact duration of pregnancy allows you to determine the date of future birth and prepare for meeting the baby.