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 with the doctor’s term, to determine whose was more accurate.

The first movement of the unborn child is an important parameter in 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. A gynecological examination helps in identifying existing problems and determining the duration of pregnancy. Good doctors can be quite accurate (within 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 is the size of a 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 to accurately determine the abnormalities and exclude a 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 at different stages of pregnancy that 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

Pregnancy calculators

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

Calculate gestational age

Enter the first day of your last menstrual period

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. At later dates, errors of up to 2 weeks are possible.

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). Even during a healthy pregnancy, the content clearly correlates with the timing. 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 should be mentioned that finding out the gestational age, calculating and guessing the probable age of the fetus is within the competence of the obstetrician when conducting a 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.

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Firstly, in this way the woman will know when she will need to prepare to be sent to the maternity hospital. Secondly, knowing the gestational age, the doctor will be able to monitor the baby’s development, correcting possible developmental delays in a timely manner. Finally, this date will become the basis for taking maternity leave.

I would like to make a reservation right away that there is a distinction between obstetric and true pregnancy terms. Obstetricians start counting down 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, after which zygote 1 is formed and implanted in the uterus and the fertilized egg with the embryo begins to develop, and then (after 12 weeks of pregnancy) with the fetus. 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. True gestational age lags behind the obstetric one by 2 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 determine gestational age

1. According to the day of conception, which coincides with the day of ovulation. If a woman measures the temperature in the rectum (rectal temperature) or, according to indications, does an ultrasound several times during the menstrual cycle (this is necessary for drug stimulation of ovulation), then this day is precisely known. These methods are usually used by women who are being treated for infertility. Rectal temperature is measured daily at the same time - in the morning, without getting out of bed. In the first half of the menstrual cycle, the temperature does not exceed 37 degrees; on the day of ovulation, the temperature rises above 37 degrees. You cannot rely on the day of sexual intercourse: sperm enter the uterus and fallopian tubes and can live there for 3-4, and sometimes up to 7 days, waiting for the egg to leave the follicle. That is, the day of sexual intercourse does not necessarily coincide with the day of conception, and the day of ovulation is the day of conception, since the egg, after leaving the ovary, can exist for no more than a day. It follows that for women trying to get pregnant, it is better to have sexual intercourse a few days before ovulation than to be one day late.
2. It is considered reliable (up to 2-3 days) by ultrasound at the earliest stages - up to 6-7 weeks, when the embryo grows proportionally and its size in all women with the same gestational age will be identical. When carrying out subsequent ultrasound examinations, the size of the fetus will vary in patients from different ethnic groups, with different body weights, the weight of the mother and father at birth will matter, and so on. That is, at a later date, normally developing children of the same “age” can have different sizes (within + 3 weeks).
3. By date of last menstruation. This is also a reliable count, but for women with a regular menstrual cycle. If menstruation is delayed, it is necessary to compare pregnancy terms according to various indicators. Find out approximate due date It is possible if you add 280 days to the day of your last menstruation. To make the calculation easier, a formula was invented: -3+7. You need to subtract three months from the month in which your last menstruation occurred, and add seven days to the number of your last menstruation. For example, if the last menstruation began on June 20, then expected due date at (exactly 40 weeks) will be March 27; if October 2, then you should expect an addition to the family on July 9.
4. At the first movement of the fetus. It's not very accurate determination of gestational age. Women begin to feel the movement of the baby at 18-20 weeks. Thus, for determining the due date 20-22 weeks must be added to the date of the first movement. However, multiparous or thin patients may feel fetal movement as early as 16 weeks.

Defining due date, the doctor usually uses not one, but several methods: this increases the reliability of the calculation. At the same time, determination by the date of ovulation and early ultrasound is considered the most reliable.

However, the child’s birthday does not always coincide with the date given by the doctor. But the reason is not a calculation error. The fact is that the period of gestational development (intrauterine life) of the fetus can range from 37 to 42 weeks. This period depends on many factors, but primarily it is determined genetically. Therefore, when establishing the estimated date of birth, the doctor may ask at what week of pregnancy the patient and the child’s father were born, as well as to what period the pregnancy of the maternal relative was carried to term. Therefore, if you gave birth a little earlier or later than your due date, you have no reason to worry.

1 Zygote - (from the Greek zyg?tós - joined together), a fertilized egg; a cell formed in animals and plants as a result of the fusion of male and female reproductive cells; the initial stage of embryo development.

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 long your pregnancy is in various ways, their advantages and disadvantages.

By conception

Pregnancy occurs when the egg and sperm fuse. This happens 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, a gynecological examination is performed. It helps to identify possible problems and determine the gestational age, and sometimes the location of the fetus (we must not forget that the embryo does not always develop in the uterus). So, with a manual examination of the expectant mother at 5-6 weeks (3-4 weeks of delay), the uterus is only slightly enlarged, its size can be compared to the size of a 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 .

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Gestational age- one of the main components that a gynecologist needs to know about for proper management of pregnancy. After all, on the basis of this, the doctor will prescribe the necessary examinations, tests, routine ultrasounds, monitor intrauterine growth and development of the fetus, and identify possible violations during the pregnancy. In addition, determining the due date allows you to fairly accurately calculate the date of birth and the date of maternity leave. It is necessary for the woman herself to know the duration of her pregnancy in order to mentally prepare for childbirth, have time to prepare a room or corner for the unborn baby, and purchase all the necessary accessories and clothes for him.

In this article we will look at how to determine the duration of pregnancy.

Calculate by monthly

For a woman who comes to register at the antenatal clinic, the gynecologist first of all asks a question about when her last period began. It is from this date that he begins to keep a record, despite the fact that fertilization has not yet occurred. It is known that fertilization of the egg occurs on the day of ovulation, which occurs in the middle of the menstrual cycle. This method of determining the gestational age is called “obstetric”.

An online calculator will help determine the period:

How to determine the gestational age by the date of conception

It is known that conception occurs only during ovulation within 24 hours after the egg leaves the follicle. And the viability of sperm in the female genital tract is up to 3 days. It turns out that the date of sexual intercourse does not always coincide with the date of conception.

Ovulation occurs in the middle of the menstrual cycle. A woman who monitors her menstrual cycle can quite accurately calculate the onset of ovulation. In addition, many at this time develop characteristic symptoms: aching pain in the lower abdomen, breast swelling, irritability, copious vaginal discharge, increased libido.

It is worth noting that only those women who have a regular menstrual cycle can determine the gestational age by the date of conception.

Online calculator:

(calculation will take a few seconds)

How to calculate using ultrasound

It is possible to find out the gestational age using the results of an ultrasound examination (ultrasound). It is determined according to the size of the fetus. The first ultrasound of the expectant mother is performed at 12-14 weeks, but it is still impossible to determine the exact date, since the development of the fetus occurs individually in each woman. It is possible to find out the age of the fetus by ultrasound with an accuracy of one day only in the first weeks after conception.

Determination during examination by a gynecologist

A gynecologist can determine a woman's gestational age by the size of her uterus during a gynecological examination. At 5-6 weeks, the size of the uterus can be compared to a chicken egg, at 8 weeks - to a goose egg. Later, it will be more difficult to determine how many weeks a woman has based on the size of her uterus.

Find out the due date by the first fetal movement

In the first pregnancy, a woman begins to feel fetal movements at 20 weeks, in the second - at 18 weeks. But this method does not always allow one to determine the period, since some expectant mothers may feel the first movements of the fetus earlier or later than the indicated weeks - some, due to the structural features of the body, cannot feel the movements of the fetus, others confuse the work of the intestines (increased gas formation) with movements.

Determine by hCG

Human chorionic gonadotropin (hCG)- one of the most important indicators indicating the onset of pregnancy and its normal development. The hormone begins to be produced in the female body after implantation of the embryo into the wall of the uterus. The level of hCG in the blood allows you to find out the approximate age of the fetus. With multiple pregnancy, the level of the hormone in the blood increases in proportion to the number of fetuses.