Today, the development of medicine and scientific technologies make it possible to accurately diagnose and predict the state of human health. This also applies to pregnancy. A few decades ago, no one could predict the exact date of birth, the gender of the baby, but today this is quite common information that a pregnant woman can receive during a routine examination by a gynecologist. Currently, it is possible to determine how many weeks of pregnancy using several methods, and without the help of a doctor. The revised data will be reported by the gynecologist after the ultrasound. So, the article will discuss the ways in which you can set the term for an interesting position.

Why do you need to know the gestational age?

First, to calculate the estimated due date. Secondly, in order to competently monitor the development of the baby, in time to correct the lag in development and formation. Third, to determine the start date of maternity leave. Knowing the exact period of pregnancy allows you to timely identify anomalies and pathologies of the baby's development (for example, Down's syndrome).

You should know that there is a difference between true and obstetric terms. Obstetricians-gynecologists count the beginning of pregnancy from the day when the last period began. This is justified by the fact that this is the moment of the beginning of the maturation of the egg, which, as a result of fertilization, is introduced into the uterus and begins to develop. The duration of pregnancy in obstetric terms is 40 weeks, or 280 days. But there are deviations, it all depends on genetic factors. The time at which the woman herself was born, as well as the father of the child, affects.

The true period from obstetric differs by two weeks, while the countdown of pregnancy begins from the day of ovulation or conception. So, let's look at a variety of methods on how to determine how many weeks of pregnancy.

Pharmacy test

The most common way to determine how many weeks of pregnancy is through a test. With its help, you can establish the presence of pregnancy. They are all based on the analysis of the presence of the hCG hormone, the content of which increases with increasing gestational age. The more sensitive the test, the earlier the pregnancy can be confirmed. The highest quality and most sensitive test can establish a pregnancy approximately 7-9 days after the intended conception.

Types of tests:

Reservoir. The test is placed in the analysis reservoir and the strip on the test determines how much urine needs to be drawn for an accurate test.
Cassette. It resembles a device with a recess in the middle, where a drop of urine is introduced with a pipette.
Jet. During urination, it must be brought under the stream of urine.
Digital. It is a device with a hole that is moistened with urine.
Strip test (most common). It is a strip that is immersed in any container filled with urine up to the level set on the test.

Method for determining the gestational age by the date of ovulation

During ovulation from the ovary, a mature egg begins to move along the fallopian tube, and it is at this time that there is a maximum chance of getting pregnant. By the date of ovulation, you can establish the true gestational age, and it usually occurs in the middle of the cycle.

But how to determine how many weeks of pregnancy by ovulation? How do you know when it happened? There are several ways to determine the onset of ovulation:

With the help of ultrasound.
At home, with tests that can be purchased at the pharmacy.
By measuring basal temperature. At the beginning of the cycle, it is below 37 ° C, the day before the onset of ovulation, it decreases, and on the day of ovulation and the entire second phase of the cycle, up to menstruation, it will keep 37 ° C and above.

There are hypersensitive women who, according to their sensations, can determine their ovulation: soreness in the abdomen, increased discharge, increased libido, and so on. It is much easier for these women than for others to determine on their own the term of an interesting position.

Method for determining the duration of pregnancy by the last menstruation

The most common way to determine how many weeks of pregnancy is the obstetric method - by the day of the beginning of the last period. To this day, add 280 days and set the approximate date of birth. That is, if, after a delay, you go to the antenatal clinic with confidence that the pregnancy is 5 weeks, the doctor will set a period of 7 weeks - this is the obstetric period.

Female doctor

The most accurate way to determine how many weeks you are pregnant is by consulting your doctor. If you contact early dates (4-5 weeks), the doctor will have no difficulty in setting the exact time. He will measure the uterus, and then calculate the gestational age. For example, at 4 weeks, it is about the size of a chicken egg, at 8 weeks - a goose. An experienced doctor is able to set the deadline for a vaginal examination with an accuracy of the day.

However, after 8-12 weeks, based on the size of the uterus, it is problematic to establish the period of an interesting position. Since from the second trimester in women, the size of the uterus is very individual. That is why, when the question is asked on the forums about how many weeks it is possible to determine pregnancy and when it is better to contact a gynecologist, the answer of doctors is always the following: the earlier you contact an antenatal clinic, the easier it is to determine the duration of pregnancy.

By ultrasound

How many weeks does the ultrasound detect pregnancy? Much depends on the doctor who describes the results. But the data obtained by ultrasound before the 12th week of pregnancy are considered the most correct. According to them, you can name the date of the alleged birth. At this time, they are based on the measurement of the ovum and its diameter. In the second and third trimesters, they are based on determining the circumference of the baby's head, on the average diameter of the tummy and chest. But the information obtained by measuring the head circumference is considered the most accurate.

It is believed that the longer the gestation period, the more difficult it is to determine it using ultrasound. Because every child is different, and at the end of pregnancy, its parameters may differ greatly from the standard.

At the first stir of the baby

There is another method. How many weeks can pregnancy be determined? This can be recognized by the movement of the baby. Primiparous women begin to feel the movements of the baby for the first time at a period of about 20 weeks. Those women who have already given birth feel their baby a little earlier - at 17-18 weeks. This method of determining the gestational age is not entirely accurate. There are women who begin to feel the baby's movements in their first pregnancy at 16 weeks. This happens most often in thin girls.

By basal temperature

The method is suitable for those women who constantly monitor the basal temperature, and not only on the day when pregnancy is suspected. The method consists in measuring the body temperature in the rectum (rectally), vaginally or orally for 5 minutes every day. The main condition is that this is done immediately after waking up and before getting out of bed. Always use only one permanent measurement site, for example, orally. What is the essence of this method?

The menstrual cycle is divided into two phases: follicular and luteal. The first lasts from the beginning of menstruation until ovulation, the second after ovulation. In the first half of the cycle, the basal temperature is always lower than during the luteal phase. During ovulation, the temperature rises and then gradually begins to decrease until the onset of menstruation. But if the temperature in the second half of the cycle does not decrease, but even increases slightly, then this clear sign pregnancy. After how many weeks can pregnancy be determined using this method? Literally through, it will become clear that the temperature does not decrease, and by the time of the delay it will already be reliably known about interesting position.

HCG

This is the most accurate method. It allows you to detect pregnancy as early as 8-10 days after conception. In a woman's body, the hCG hormone begins to be produced immediately after the introduction of a fertilized egg. This hormone is present in the urine and blood of the expectant mother, and to establish the presence of pregnancy, you can donate blood for analysis or take a test.

It should be borne in mind that the period of pregnancy in terms of the level of hCG in the blood does not coincide with the obstetric period, since this hormone begins to grow from the moment the embryo is fixed (that is, from the true gestational age).

Folk methods

The urine of a pregnant woman has an alkaline reaction, if you add soda to the morning portion, it will settle. But if the woman is not pregnant, the urine will bubble as a result of the reaction.

Online calculators

There are a huge number of calculators on the Internet with which you can create your pregnancy calendar. It is necessary to enter the day of the beginning of the last menstruation in the window of such an online test, after which the program will provide a detailed calculation of the growth and weight of the fetus by week.

Instead of a conclusion

All of these methods can accurately determine the presence and duration of pregnancy. But it should be borne in mind that the baby, even with the most correct calculations, may be born later or earlier than the due date. Natural childbirth can occur from 38 to 40 weeks, but premature birth can occur, or, conversely, the baby may be born at 41 weeks. Everything is individual, depends on many factors, the main of which are genetic predisposition and the presence of chronic diseases. Be that as it may, the main task of the mother is to do everything that depends on her so that the pregnancy goes well, and the daughter or son is born safely.

It is very difficult to calculate the gestational age with an accuracy of the day and is possible, perhaps, only if ovulation was specifically monitored using ultrasound. But these procedures are carried out only in the treatment of infertility. Therefore, the day of conception often remains a secret even for the couple themselves, not to mention the doctors.

And yet, there are any calendar methods for calculating conception, can the gestational age be calculated based on the menstrual cycle and the day of delay? What procedures and analyzes help in diagnosis and calculations? You will read about all this in the article.

Calendar methods

If sexual intercourse does not occur too often, then it is quite possible that a woman will remember exactly on which day the very nimble sperm, which subsequently fertilized the egg, entered her body. This is also possible if a woman scrupulously measures basal temperature over several cycles and knows how to use the obtained graphs with temperature values. She informs the doctor about this most calculated day, after confirming her pregnancy. However, the doctor, having found out when the last monthly patients were, calls the period 2 weeks longer. How can this be and what to believe?

The fact is that doctors consider the obstetric term, and it depends only on the first day of the last menstruation. It turns out that pregnancy begins on the first day of menstruation, although this is not the case, of course. But this calculation technique turns out to be quite accurate. And according to the same technique, the estimated date of birth is calculated: 280 days are added to the first day of the last menstruation, or 3 months are taken away and 7 days are added (according to the Negele formula).

If the day of ovulation is known exactly, then you can add not 280 days to the first day of the menstrual cycle, but 264. And in this way we also find out the estimated date of birth. Well, pregnancy can be started from the day of ovulation. But again, doctors do not conduct such a calculation, and these values \u200b\u200bare not taken into account.

Ultrasound procedure

For many years, ultrasound has been actively used to diagnose fetal development. And with the help of ultrasound, the gestational age is specified. Studies carried out in the first weeks of pregnancy (up to 8 weeks) are especially accurate in this regard. During this period, all healthy embryos develop in the same way, and the gestation period according to the size of the fetus is set exactly up to the day. The longer the period, the more mistakes, since the children begin to show individuality in a certain sense - one may have a slightly larger head than it should be at a certain time, and the other baby has a growth slightly below their age limits. If the deviations are insignificant - for a week or less, then their doctors do not take into account, as a rule, and nothing needs to be treated. The estimated date is based on the measurement data of the coccygeal-parietal size. The result is obtained using a table.

If there is a delay in development for 2 weeks or more, with all that there is confidence in the absence of an error in setting the gestational age, the doctor diagnoses "intrauterine growth retardation." It is impossible to "cure" it. Everything that is done in the hospital has only a preventive, and not too pronounced, effect. Good food, healthy image life, walks, quiet leisure - that's what is much more important.

Gynecological examination

Many women go to the gynecologist on the very first day of the delay, or even earlier, in the hope that the doctor will be able to say for sure whether they are in a position or not. Unfortunately, this is not possible. The uterus may be slightly enlarged before menstruation. The growth of the uterus due to the development of the fetus in it begins significantly from the end of the first trimester. At 5-6 weeks (that is, in the second or third week of missed menstruation), the uterus is slightly larger than its usual size, the volume can be compared with 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. Again, the shorter the gynecological examinations, the more accurate it is to determine the gestational age.

Date of the first stir

All gynecologists inspire their patients, expectant mothers, that they must remember the day when they first felt the baby inside themselves, that is, they felt his movements. It is believed that in pregnant women for the first time this happens exactly at 20 weeks of pregnancy, and in pregnant women again - at exactly 18 weeks. This date must be included in the dispensary card of a pregnant woman and is taken into account when determining the expected date of birth. Although, if you believe the statements of many expectant mothers, the timing of the first movements do not always coincide with the "book" ones. I would also like to reassure the hyperresponsible expectant mothers a little, who fear that they will not notice the first movements, thereby confusing the doctor when setting the date of birth, which can lead to prolongation. Firstly, overmaturity is determined by the result of Dopplerometry and by some ultrasound indicators (maturity of the placenta, volume amniotic fluid etc.). And secondly, the first movements are really very light, but quite tangible. It is impossible not to notice the movement if you are in horizontal positionespecially on the back.

Uterus length

From about the second trimester of pregnancy, and sometimes even earlier, gynecologists evaluate the development of the fetus along the length of the uterus. It is measured with a centimeter tape, the expectant mother lies on the couch. Each week adds approximately 1 centimeter. There is one more measurement technique, many doctors use appropriate plates, and they can also be found in manuals on obstetrics and gynecology.

12 weeks - uterus at the upper edge of the bosom

14 weeks - the uterus is two fingers above the bosom

16 weeks - the bottom of the uterus is felt between the navel and the bosom

20 weeks - the fundus of the uterus two fingers below the navel

24 weeks - uterus at navel level

28 weeks - the fundus of the uterus 2 fingers above the navel

32 weeks - between the navel and the xiphoid process (the shortest part of the sternum), length 28-30 cm

36 weeks - the fundus of the uterus at the level of the xiphoid process, "props up" the ribs, length 32-34 cm

40 weeks - before childbirth, the uterus drops to the level of 32 weeks, as the baby's head (or other presenting part of the fetus) moves lower into the pelvis, prepares for exit.

In addition to the length of the uterus, the volume of the abdomen is also taken into account, but these sizes are already more variable, they do not always show the true state of affairs and help to calculate the gestational age by weeks. The volume of the abdomen is measured at the level of the navel. So in a woman with a normal weight before and during carrying a child, the volume of the abdomen at 32 weeks will be approximately equal to 85 centimeters, and by the end of pregnancy it reaches 90-100 cm. Such an increase is associated with the rapid weight gain of the child.

The length of the uterus not only helps to ensure the normal development of the fetus, gestational age, but also to detect pathologies such as polyhydramnios or oligohydramnios and others in time.

Heart tones

The child's heart begins to beat already at a period of 4.5 weeks, that is, 2-3 weeks after the start of a delay in menstruation in a woman. Heartbeats are visible on an ultrasound scan, and this is the main sign that the embryo is alive and developing. Later, the doctor begins to listen to the heartbeat through the outer wall of the uterus. But you can only hear heart tones not at 10-12 weeks, but later - at about the same time as you feel the first movements. The heartbeat is listened to using an obstetric stethoscope - a special tube that the doctor applies to the patient's abdomen. The heartbeat can be poorly heard for several reasons. The most "harmless" of them - the placenta, which is located on the front wall of the uterus, and thereby drowns out the sound and significant deposits of fat on the abdominal wall. More serious - polyhydramnios, chronic hypoxia. The longer the period, the more clearly the heart rhythms are heard.

Chorionic gonadotropin level

This method of determining the gestational age is used, as a rule, in the first weeks. But it does not always give an accurate result. A blood test is taken from a vein.

Approximate HCG values \u200b\u200bfor the first weeks of pregnancy:

2 - 25-300 mU / ml
3- 1500-5000 mU / ml
4 - 10,000 - 30,000 mU / ml
5 - 20,000 - 100,000 mU / ml

As you can see, the values \u200b\u200bcan vary greatly, so calculation errors are possible. This analysis is ideally used not to calculate the timing, but for the early diagnosis of pregnancy and its possible pathologies.

We have given the main ways of how to correctly calculate the gestational age. Some of them can be tried on their own, while others require medical intervention and procedures.

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Firstly, in this way the woman will know when she will need to prepare to be sent to the hospital. Secondly, knowing the gestational age, the doctor will be able to monitor the development of the baby, correcting possible developmental lag in time. Finally, this date will become the basis for obtaining maternity leave.

I want to make a reservation right away that they distinguish between obstetric and true terms of pregnancy... Midwives start counting down gestational agefrom the 1st day of the last menstruation. This is quite justified, because from this moment the egg cell begins to mature, which will be fertilized by the sperm in the future, after which it is formed and implanted into the uterus of zygote 1 and the ovum 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 menstrual period to delivery is about 10 lunar months, or 280 days, or 40 weeks. True gestational age lags behind obstetric 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 the gestational age

By 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 scan several times during the menstrual cycle (this is necessary for drug stimulation of ovulation), then this day is known for sure. These methods are usually used by women who are being treated for infertility. Rectal temperature is measured every day at the same time - in the morning, without getting out of bed. In the first half of the menstrual cycle, the temperature is not higher than 37 degrees, on the day of ovulation, the temperature rises above 37 degrees. It is impossible to navigate by 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 release of the egg from 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 cell after leaving the ovary can exist for no more than a day. From this it follows that it is better for women seeking to become pregnant to have sexual intercourse a few days before ovulation than to be one day late.
Reliable (up to 2-3 days) is considered 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 conducting the next ultrasound examinations, the size of the fetus will differ 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, more late dates normally developing kids of the same "age" can have different sizes (within + 3 weeks).
By the date of the last menstruation. This is also a valid reading, but for women with regular menstrual periods. With delays in menstruation, you need to compare terms of pregnancyby various indicators. Find out the approximate due date it is possible, if 280 days are added to the day of the last menstruation. To facilitate the calculation, a formula was invented: -3 + 7. From the month in which the last menstruation was, you need to subtract three months, and add seven days to the number of the last menstruation. For example, if the last menstruation began on June 20, then estimated date of birthin (exactly 40 weeks) will be March 27; if it is October 2, then the addition in the family should be expected on July 9.
By the first movement of the fetus. It's not very accurate determination of the gestational age... Women begin to feel the movement of the child at 18-20 weeks. Thus, for determining the due dateit is necessary to add 20-22 weeks to the date of the first stirring. However, multiparous or thin patients can feel fetal movement as early as 16 weeks.

By defining due date, the doctor usually uses not one, but several methods: this increases the reliability of the count. In this case, the most reliable are determined by the date of ovulation and by early ultrasound.

However, the child's birthday does not always coincide with the date given by the doctor. But the reason is not a miscalculation. 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 first of all it is determined genetically. Therefore, when establishing the estimated date of birth, the doctor may ask in which week of pregnancy the patient herself and the father of the child were born, as well as to what time the relatives carried the pregnancy. maternal line... Therefore, if you gave birth a little earlier or later than the appointed time, you have no cause for concern.

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 germ cells; the initial stage of development of the embryo.

Every expectant mother wants to know the exact period of pregnancy. Having determined it, you can calculate the date of birth of the baby. It is important for a doctor to know the gestational age in order to monitor the growth and development of the fetus, because each period of pregnancy corresponds to certain indicators of the rate of its course and the size of the child. Let's consider how to find out the exact duration of pregnancy.

Obstetric and true timing of pregnancy

Many women while waiting for a baby have heard such a term as "obstetric term". What is he like?

The obstetricians consider the first day of the last menstrual period to be the starting point for pregnancy. They explain this by the fact that from this moment the maturation of the egg begins, which in the future will be fertilized by the sperm, then a zygote will form, penetrate into the wall of the uterus, and the embryo will begin to develop. Doctors note that the duration of the gestation period from the first day of the last menstrual period to the moment of delivery is about 280 days or 40 weeks. However, the normal fetal development period is 37-42 weeks, since each child develops in its own way. The duration of its development depends on many factors, the main of which is heredity.

The actual gestational age is two weeks less than obstetric. It is calculated from the day of ovulation and conception. To determine the obstetric period, 14 days are added to the true one.

How to determine the exact date using medical methods

At the very beginning of pregnancy, for a period of 3-4 weeks, an experienced doctor can set the period with an accuracy of 1-2 days. To do this, he conducts a vaginal examination and determines the size of the uterus, which increases every day of pregnancy. However, this is possible only in the early stages, but after 8-12 weeks, the exact duration of pregnancy cannot be established during a gynecological examination. At this time, the size of the uterus differs from woman to woman.

How else to find out the exact term using medical methods? Of course, this can be done by ultrasound. The accuracy of determining the term in this case will depend on the qualifications of the doctor. The most correct period is considered to be before the 12th week of pregnancy. Its determination is based on measuring the size of the ovum, more precisely, its inner average diameter.

To establish the term in the second and third trimesters, parameters such as the circumference of the fetal head, the circumference of the abdomen of the fetus, the average diameter of the tummy and the head of the fetus are determined. The most accurate measurement is the circumference of the fetal head. But with the course of pregnancy, the possibility of errors in establishing the exact date increases. This is understandable, because each baby in the womb develops depending on its individual characteristics.

In the second half of pregnancy, the doctor can determine the term by measuring the length of the uterus. For this, a woman, having previously emptied her bladder, lies down on the couch, straightening her legs. The gynecologist measures the length of the uterus using a pelvis meter or a measuring tape. Its size during this period corresponds to the due date. So, if the length of the uterus is 35 cm, this means that the period is 35 weeks of pregnancy.

How to calculate the exact term at home

Pregnancy test

It is easiest to determine the term at the beginning of pregnancy using a pharmacy test. Its principle of action is based on the determination in the urine of the hormone human chorionic gonadotropin (hCG), which is present only in the body future mother... From the moment of conception, its amount doubles every two days. The highest concentration of hCG is observed at 8-10 weeks of pregnancy. Most tests have three options for determining the term - 1-2 weeks, 2-3 weeks, 3 weeks or more.

Method for determining the date of ovulation

You can use the method of determining the date of ovulation. During ovulation, the female egg leaves the ovary into the fallopian tube and "waits" for the sperm there. Unprotected sexual intercourse at this time in a healthy woman usually leads to conception. Ovulation in women occurs in the middle of the monthly cycle. So, if the duration of the menstrual cycle is 30 days, then ovulation usually occurs on 15-16 days. From this moment, you can count the gestational age.

To determine the day of ovulation, there are special tests that can be purchased at the pharmacy. You can also use basal temperature measurement. Some women determine their day of ovulation by their feelings - increased libido, pain in the lower abdomen, an increase in the amount of vaginal discharge.

On the day of the last menstruation

An easier way to determine the duration of pregnancy is by the day of the last menstruation. In this case, 280 days are added to the first day of the last menstruation and the date of birth is determined. Doctors sometimes use the Negele formula that every woman can use. According to it, three months are subtracted from the start date of the last menstruation and seven days are added. You need to know that this method is only effective for women with regular menstruation.

Baby wiggle

It is worth mentioning such a method for determining the duration of pregnancy, as the first movement of the baby in the womb. It is known that those women who are preparing to become a mother for the first time feel the first stir at 20 weeks. And multiparous people experience their baby for the first time at 18 weeks. However, this method cannot be considered very accurate. Feelings of expectant mothers are quite subjective, and for the first time they can feel the baby both at 17 weeks and at a later date. It was also noticed that thin women first feel the child earlier than plump expectant mothers.

The need to calculate the gestational age by weeks arises in almost every pregnant woman and more than once during pregnancy. And this is necessary not only in order to simply know your due date or correctly track the pregnancy calendar. I also want to calculate the duration of pregnancy and childbirth in order not to doubt the correctness of the doctor's actions, if the consultation is mistaken - this can also affect the date of maternity leave, I don’t want to work an extra couple of weeks, right?

First, some general information.

Our calculator will help you calculate the obstetric gestational age, it does not correspond a little to the real life of the fetus. Gynecologists base all their calculations on the date of the first day of the last menstruation, and do not count from fertilization, this is due to the ease of error in the date of conception.

Ovulation in a woman can significantly shift in time, especially if she does not have a regular cycle, and of course, not everyone can know the exact date of fertilization, it is difficult to calculate the gestational age by ovulation. And the start date of the last menstrual period is usually known.

We have a special calculator that allows you to independently calculate your pregnancy period online. He will give you information not only about the obstetric gestational age, but also the date of conception, the age of the fetus, the date of birth.

The problem may arise if you do not have it regularly. How to correctly calculate the period of pregnancy by menstruation with an irregular cycle? You need to add the length of the last 6 cycles and divide by 6, so you get the average duration, this is the number of days and you need to enter in the calculator field.

All received data can be easily controlled using other calculation systems.

You can accurately calculate the gestational age (well, or relatively accurately, as gynecologists believe) using the Negele formula. It does not take into account the length of your cycle, and therefore the result may differ from the period that our calculator will give, but this will certainly coincide with the calculations of the gynecologist: we subtract 3 months from the first day of the monthly delay and add 7 days to the resulting date. This is your due date. Calculating the gestational age by months, weeks and days, as with our calculator, will not work with this formula.

If you had an ultrasound scan, the doctor measured your baby's developmental indicators. Its weight, the length of the bones allow us to calculate the gestational age by ultrasound, but this calculation is accurate only in the first trimester, the longer the period, the greater the difference in physical development in different children, and the risk of error in determining the timing of pregnancy is higher.

Almost all calculation methods carry a certain risk of error, therefore, only 4% of children are born in the PDD (preliminary date of birth).

It is better to evaluate the calculation results in a complex (ultrasound, date of the last menstruation, first stirring and other dates and signs). Still, the due date can be between 37 and 42 weeks of gestation.

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