How does a doctor determine the period? How to find out the exact and correct gestational age? True pregnancy

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 baby’s development, 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 (after 12 weeks of pregnancy) will begin to develop. The duration of pregnancy from the first day of the last menstruation until birth is about 10 lunar months or 280 days or 40 weeks. However, each fetus has its own period of intrauterine development - from 37 to 42 weeks. This depends on many factors, but is primarily determined genetically. It is necessary to ask at what stage of pregnancy the patient herself, the father of the child was born, and until what period the pregnancy of the maternal relative was carried to term.
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, a mature egg is released from a woman’s ovary into the fallopian tube and “awaits” sperm there. Unprotected sexual intercourse at such a time in a more or less healthy woman and man 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 to a chicken egg, at 8 weeks - to 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, determining the gestational age is based on measuring the fetal egg and its average internal diameter.
In the second and third trimesters, the gestational age is determined based on the determination of such parameters as the circumference of the fetal head, the average diameter of the fetal chest and abdomen, and the circumference of the fetal abdomen. 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, it is necessary to add 20 weeks (or 4.5 months) to the date of the first movement; for multiparous women, it is necessary 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 than the due date of 20 weeks, 17 weeks, or even earlier. Especially often such early movements are observed in thin women. There are women who feel the first movements 2 weeks later than expected.
Doctors have their own opinion regarding 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.

It is possible to calculate the gestational age even more in a complicated 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 there may be errors in determining the correct gestational age. 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.

After all, determining this period will help calculate the approximate date when the long-awaited child will be born. There are a lot of methods, and it’s hard to say which one is the most accurate. But it is quite possible to determine what week of pregnancy you are in at home.

Medical examination methods

Let's look at how doctors determine the gestational age:

According to ultrasound. This is one of the most common methods. The doctor measures the size of the fetus and uses it to tell you approximately your due date.
By date of last menstruation. This way you can determine when ovulation occurred
According to the size of the uterus. With each week of pregnancy, the uterus changes, increases in size and rises higher.
HCG analysis. It shows the amount of hormones in the blood. The method is quite accurate, but still does not give an unambiguous result.

Pregnancy: how to determine its duration at home

Some women prefer not to immediately contact doctors because they know how to find out if they are pregnant early stages at home. There are a considerable number of methods, here are some of them:

By date of ovulation.
According to the last menstruation.
According to the baby's movements.
By date of conception.
Naegele's formula.

Determining pregnancy at home in the early stages

If you don’t have a test at hand, there are other ways to find out if you are pregnant in the early stages at home:

Using baking soda.

Take a small container and fill it with morning urine. Add a spoonful of soda there and watch carefully what happens. If the baking soda reacts and starts to fizz, it means you are not pregnant. And if it precipitates, it means you will soon become a mother.

With the help of iodine.

You will need a container filled with morning urine. You need to add a small drop of iodine to it. If the drop remains on the surface, then you are pregnant, but if it dissolves, then you are not.

Ovulation: how to determine the gestational age by it

Ovulation is the period of the menstrual cycle when a woman can become pregnant. At this time, the egg matures, then exits into the fallopian tube and remains there for a certain period of time in order to wait for sperm.

If you want to understand how to find out the gestational age by the date of ovulation, then you must have a chart for maintaining basal body temperature. By the way, in pharmacies you can find tests that help accurately determine ovulation. If sexual intercourse occurs during this period, then most likely you are pregnant.

We determine the period based on the last monthly

Finding out the gestational age by the last menstruation is another method that you can use at home, without the help of doctors. The first day of the last menstrual cycle is the period when the egg matures, the body is completely rebuilt and conception is currently as possible as possible.

Finding out the gestational age from the last menstruation is very simple. Count how many weeks have passed from this date to now - that's all.

Take a calendar and add 280 days to this date. This is approximately 40 weeks (this is how long the pregnancy itself lasts). It will work out approximate time, you must give birth to your child.

The easiest way to find out the gestational age is by the last menstruation. It is for this reason that women use it at home. Not everyone can measure their basal temperature and determine the period of ovulation, but everyone records the start date of menstruation.

When the baby starts to move in the womb

Any representative of the fair sex who is preparing to become a mother is very sensitive to the period of bearing a baby. Many questions arise regarding pregnancy and childbirth. Some people try to find out the gestational age by their periods, others use other methods.

It is worth noting that it is almost impossible to determine the exact period. But if you count it in several ways, the probability will increase. For example, you have already calculated your period based on your period, now wait until you feel the baby’s first movement.

In primiparous women this usually occurs at 20 weeks, in multiparous women it may be earlier. In any case, when you feel the baby begin to move in the womb, you will know that you are now approximately 20 weeks pregnant.

Date of conception: how to use it to calculate gestational age

Determining which week of pregnancy you are currently in is only possible if you know exactly the date when conception occurred. Otherwise, only a gynecologist can do this.

To find out the duration of your pregnancy by weeks and days, sign up for an examination, the doctor will find out from you the date of the first day of your last menstrual period and calculate the obstetric period and name the approximate date of birth. Please remember that this is only an approximate date. Only your baby knows when he will be born. It is possible to find out the gestational age by weeks and days quite accurately, but you should not rely on the date of birth.

Naegele's formula

The Naegele formula is the easiest way to find out the approximate date of birth.

Take the first day of your last period and subtract three months from it.
7 days are added to the resulting date.
The final date is the approximate time when the baby will be born

The exact date of pregnancy - is it possible to find out?

Most women are interested in the question of how to find out the exact date of pregnancy. Doing this at home is problematic, because any method gives deviations from the truth. If you want to get more reliable information, you can do this in the following ways:

Ultrasonography.

Ultrasound can show the exact date only in the early stages. The fact is that embryos develop equally only in the first 3-4 weeks after conception occurs. Further, the embryo develops differently in each girl.

Gynecological examination.

How to find out the exact date of pregnancy during a gynecological examination? The doctor measures the uterus and sometimes even determines the position of the fetus at this stage. Based on the data obtained, you can understand what week of pregnancy a woman is in, because the uterus is constantly changing and there are standards for how this should happen.

Boy or girl

An ultrasound examination is not yet done soon, but the expectant mother is already overwhelmed with interest in who she will give birth to - a boy or a girl? It is worth noting that ultrasound sometimes fails to determine the sex of the child. Some parents are happy about this because they want a surprise, while others, on the contrary, want to know everything at once.

You can find out the sex of the child in the early stages of pregnancy in the following ways:

According to the intensity of sexual life.

If the conception of a child occurred during a period when the couple was sexually active, then it is more likely that a boy will be born. The fact is that mobile “male” sperm do not live very long. Therefore, when a man rarely has sexual intercourse, the body experiences greater vitality of “female” sperm. This has been proven scientifically.

By blood purity.

The gender of the child is very often determined depending on which spouse has newer blood. It is believed that in women the blood is renewed once every 3 years, and in men once every 4 years. If at the time of conception the man’s blood is newer, it means there will be a boy, if the woman has a girl.

According to the formula.

Our grandparents very often used a formula to determine the gender of their unborn child. It looks like this: 49-X+1+Y+3. Y is the month when conception occurred, and X is the father's age. Substitute all the data and calculate what happens. If the number is odd, it means there is a higher probability that a girl will be born, and if it is even, it means a boy.

By woman.

They say that if a woman becomes prettier during pregnancy, then she is expecting a boy, because boys take care of their mother and give her beauty. With girls the situation is the opposite, they take away beauty. Therefore, if you notice that your hair has become thinner, your nails are peeling, your skin is dry - this means that, most likely, you will give birth to a representative of the fair sex.

Which method is the most accurate?

Every woman is interested in how to find out the duration of her pregnancy, and at least the approximate date when she will give birth. All of the methods listed above are good in their own way, but none of them can give you a clear answer to this question.

The fact is that each representative of the fair sex is special, just like her body, and only he himself knows when the baby decides that he is ready to be born. This may happen several weeks earlier if the fruit is ripe. If the baby is not yet ready to leave the mother's womb, then the pregnancy is delayed for several more weeks.

Now you know how to find out your gestational age at home, just like doctors do. Moreover, if the ultrasound does not show the sex of the child, then thanks to the methods listed above you can determine it yourself. Even if the result turns out to be unreliable, it is still interesting. After the baby is born, you will be able to determine which method turned out to be true for you.

There are several ways to find out the gestational age: some of them are not very accurate, but are convenient and accessible to every woman, others require special examinations. It is necessary for doctors and their pregnant patients to know the exact date in order to competently monitor the development of the child, notice possible developmental pathologies in time and correct them, and also calculate the date of the upcoming birth as accurately as possible. Let's look at how to find out how far into pregnancy you are different ways, their advantages and disadvantages.

By conception

Pregnancy occurs when the egg and sperm fuse. This occurs within 1-2 days after ovulation. Some women feel ovulation, because it has quite noticeable symptoms (stretching mucous discharge from the cervix, strong libido, tingling in the lower abdomen, in the ovarian area), other ladies use special ovulation tests (some as contraception for excluding sexual intercourse on “dangerous” days, some on the contrary to speed up conception), others measure basal temperature for this purpose (cheap and cheerful). But even if it is possible to accurately calculate the day of conception, and this is most likely if sexual intercourse was only once, doctors for some reason set the period at about 2 weeks longer. Some women believe that this is a sign that the embryo is “big”. But in the early stages, the size of the embryos does not differ. The whole point is that doctors determine their own obstetric gestational age, from which the date of birth is calculated. Therefore, finding out the gestational age by conception is more interesting for the woman herself than for the doctor.

Obstetric term

Let's move on smoothly to what obstetric term is and how it can be calculated. Everything is very simple. The timing of ovulation is not taken into account. All the doctor needs to know is when the first day of your last period was, and the duration of the bleeding is also not important. From this first day pregnancy begins to be considered. Thus, if you come a week after the start of the delay and are absolutely sure that your period is 3 weeks, then the doctor will give you 5 weeks. Don't be surprised by this.

By date of first movement

A very important parameter. The doctor usually writes down the expected due date depending on the “obstetric calculations” described above, ultrasound readings in the early stages, as well as the day of the first movement. Primiparous women first feel the movements of their baby at 20 weeks, and multiparous women at 18 weeks.

Ultrasonography

Usually, if there are no problems, the first ultrasound is performed at 12-14 weeks, but at this time it is problematic to establish the exact duration of pregnancy. Embryos develop equally only in the first weeks after conception, it is then that the doctor can set the period with an accuracy of 1 day. At the same time, the location of the fetus is clarified, if there is no heartbeat yet (less than 4.5 weeks), and the fetus is slightly behind in development, or any abnormalities are visible on ultrasound, it is usually recommended to repeat the study after 7-10 days to exclude missed abortion and others pathology.

Thus, it is possible to find out the gestational age by ultrasound only in the early stages. Of course, even during subsequent ultrasounds at 20.32 weeks, the form will indicate a due date in accordance with the size of parts of the fetal body and head, but do not forget that in the second half of pregnancy, children develop very individually. After all, the norm is the birth at term of both a child weighing 2800 grams and 4000 grams.

Gynecological examination

At the first visit to the doctor by the expectant mother, gynecological examination. It helps to identify possible problems and establish the gestational age, and sometimes the location of the fetus (one must not forget that the embryo does not always develop in the uterus). So, with manual examination expectant mother at 5-6 weeks (3-4 weeks late) the uterus is only slightly enlarged, its size can be compared with the size chicken egg. At 8 weeks the uterus is already the size of a goose egg. And at 10 weeks - the size of a woman's fist. After 12-14 weeks, the doctor can easily determine the size of the uterus (or rather, its length) during an examination (not vaginal) on the couch using a centimeter tape.

Here's how to find out the exact date of pregnancy. But do not forget that even with such accurate calculations, the child may be born prematurely in case of any abnormalities in the development of pregnancy, or vice versa a little (1-2 weeks) later if he is not yet fully ready for life outside the womb .

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 others negative factors. Reception medicines, 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 abortion is later 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 optimal time for abortion and preservation of a woman’s health, a period of 6-8 weeks is considered.

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

Methods for determining gestational age

Methods for determining gestational age allow you to determine how much time is left before birth and how the unborn child is developing. 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 displays 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 strips on the express test, since the digital display will show a reliable result that 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 the gestational age of the baby is to undergo a gynecological examination or ultrasonography. 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 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 have 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 controls 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 duration of pregnancy 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, the accuracy of 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 menstruation (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 do not trust the calendar method, you can check its effectiveness. Calculate the date of birth according to the calendar and check it with the one that the gynecologist says after the examination. Please note that when determining the gestational age great importance has fetal movement. 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 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, with a frozen or ectopic pregnancy, hCG is lower than normal. A sharp increase in this indicator indicates a multiple pregnancy or 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.

Days after last menstrual period	HCG levels for this period honey/ml	Gestational age

Please note that the values indicated in the table are not a standard. So, depending on the characteristics of a woman’s body and the course of pregnancy, hCG norms also change 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 ovulation period, you can buy a special test or measure 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. KTR is maximum distance from the coccyx 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:

Biparietal size, mm	Abdominal circumference, mm	Femur length, mm	Gestation period, weeks

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.

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 gestational age in 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, the expectant mother 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.

Nowadays, the development of the medical industry and technology makes it possible to make accurate diagnostics and predictions regarding the state of human health. This fully applies to the course of pregnancy. If previously no one could predict the date of birth or the sex of the child, today these are completely normal phenomena. Today, even the duration of pregnancy can be determined in several ways and even without medical participation. Let's find out about this in detail.

Why do you need to know your gestational age?

If we talk about methods for determining the duration of pregnancy, some can be called not very accurate, but convenient and accessible to most women, while others, more accurate, require special diagnostic examinations.

All these methods for determining the period serve one purpose - competent monitoring of the course of pregnancy and fetal development. Knowing the exact number of weeks of pregnancy makes it possible to timely diagnose developmental pathologies of the unborn child (for example, Down syndrome), deviations from the norm, and accurately determine the date of future birth. When the doctor knows the gestational age, then using ultrasound it is possible to compare generally accepted indicators and characteristics of fetal development with a specific pregnancy. So, let's look at ways to determine the duration of pregnancy with their advantages and disadvantages.

How to determine the gestational age by the date of conception?

Conceiving a child is the fusion of an egg and a sperm, which occurs within a day or two after ovulation. Some ladies feel it based on certain symptoms, others purchase special tests to identify it, and still others measure theirs for this purpose. Therefore, it is easiest for the category of women who feel the onset of ovulation and know the day of conception to independently determine the duration of pregnancy.

But even if you accurately calculate the day of conception (if sexual intercourse was only once), gynecologists, for a number of reasons, put the gestational age at 2 weeks longer. Pregnant women consider this a sign of carrying a large child. Unfortunately, in the first weeks the size of the embryos is almost the same. Doctors simply state the gestational age. It is used to calculate the date of future birth. Therefore, knowing your gestational age by the day of conception is interesting for the pregnant woman herself, and not for her doctor.

By the way, some expectant mothers keep their due date calendar until the end of pregnancy. Then it will be simply interesting to compare it and the doctor’s term, to determine whose was more accurate.

The first movement of the unborn child is important parameter the course of pregnancy. After all, doctors, as a rule, record the future due date depending on the ultrasound readings in the first trimester and the day of the baby. Women giving birth for the first time feel such movements at the twentieth week of pregnancy, and multiparous women a little earlier - at 18 weeks.

How do doctors determine the gestational age?

When a pregnant woman comes to the antenatal clinic for the first time, the gynecologist must examine her on the chair. Gynecological examination helps in identifying existing problems and determining the duration of pregnancy. Good doctors They can quite accurately (with an accuracy of up to half a week), as well as the location of the fetus (meaning its likely location outside the uterus).

You should know that a gynecological examination of a pregnant woman with a delay of 3-4 weeks, that is, at a period of 5-6 weeks, reveals a slightly enlarged uterus. It is approximately the same size as a chicken egg. And at 8 weeks the uterus has the size goose egg. Approximately the size of a woman's fist, she is the size of 10 weeks pregnant. Without any problems, the gynecologist determines the size of the uterus after 12-14 weeks of pregnancy. We are talking about the length of the uterus when examining a pregnant woman on the couch. In this case, the doctor uses a measuring tape.

How to determine the gestational age from the last menstruation?

Determining the duration of pregnancy by menstruation is called the obstetric period. How is it calculated?

This is not difficult, because the date of ovulation in this case is not taken into account. The duration of menstruation itself is not important. The doctor needs to know the date of the first day of the pregnant woman's last menstrual period. It is from this day that the doctor begins to calculate the gestational age. That is, if you went to the antenatal clinic one week after the delay and are absolutely sure that your pregnancy is 3 weeks, then the gynecologist will give you a 5 week pregnancy.

How to determine the gestational age using ultrasound?

Traditionally, a woman’s first ultrasound examination is prescribed at 12-14 weeks of pregnancy. But at this estimated time it is problematic to establish its accuracy. After all, the embryos of all expectant mothers develop equally only in the first weeks after conception. Then the doctor is able to determine the period with an accuracy of one day, and clarify the position of the child in the absence of a heartbeat. And if the ultrasound shows any abnormalities, then a repeat examination is prescribed after a week or ten days for precise definition deviations and exclusion of frozen pregnancy.

That is, it is possible to determine the gestational age by ultrasound only in the early stages. During the next two planned ultrasounds, doctors will set the gestational age in accordance with the parameters of the body parts of the unborn child, his head. However, we should not forget that the second half of pregnancy is a purely individual development of babies. After all, the birth at term of girls and boys weighing 2800 g and 4000 g is considered normal.

At what date will an hCG test show pregnancy?

Let us recall that human chorionic gonadotropin (hCG) is one of the most important indicators of the presence of pregnancy and its normal development. HCG is a hormone that is produced in the body of a pregnant woman after the implantation of the fertilized egg into the wall of the uterus, that is, after implantation of the embryo. This occurs already on the sixth to eighth day after fertilization of the female egg. It is the presence of this hormone in the blood and urine that is the basis for pregnancy testing. Traditional tests, which are sold at pharmacies, determine the presence of this hormone with two strips.

In the first trimester of pregnancy, this hormone stimulates the production of progesterone and estrogen. These two female hormones are necessary to maintain the normal course of pregnancy.

You should know that in the first weeks the level of human chorionic gonadotropin doubles approximately every 2-3 days. An increase of 60 percent in two days is considered normal. As pregnancy progresses, the increase in hCG levels decreases. Namely, at 8-9 weeks of pregnancy, the level of human chorionic gonadotropin stops growing. On the contrary, it begins to decline at a slow pace.

By the way, during a woman’s multiple pregnancy, the level of this hormone increases in accordance with the number of fetuses. That is, if there are three fetuses, then the hCG level is three times higher than normal. It is the standard, generally accepted norms of this hormone for different dates pregnancy are the main determinants of this period.

It should be taken into account that the gestational age based on hCG levels does not coincide with obstetric calculations. Why is this happening? The fact is that human chorionic gonadotropin determines the gestational age relative to the day the child is conceived. It essentially reflects the age of the unborn baby. But the obstetric gestational age is determined by the doctor relative to the date of the last menstruation and is not related to the date of conception of the child.

So, using the above methods you can accurately determine the gestational age. However, it is recommended to take into account that with the most correct calculations, your baby may be born earlier or later. Therefore, the main task of the expectant mother is to do everything in her power for a healthy pregnancy and the safe birth of a daughter or son.

Especially for Elena TOLOCHIK