Terms of pregnancy: obstetric and embryonic - how to determine and not get confused in terms. Why do obstetric gestational age and real

During the bearing of the first baby, a woman faces many questions. Most of them are related to how her health should be, and how to respond to certain changes occurring in her body. But in addition, many expectant mothers are faced with the problem of determining the exact gestational age. Yes, and the numbers given in the results of ultrasound and gynecological examination may differ. Usually, when calculating doctors, they use the obstetric gestational age, but in some cases the real term can also be used, let's try to figure out which calculation is right for you? And how to correctly calculate the gestational age?

In most cases, it is not possible to determine the exact date of conception, which is why, in order to understand the gestational age, doctors have always focused on the date when the last menstruation began. A similar method of calculating the gestational age is called obstetric. However, such calculations have nothing to do with the date of conception, because a new life is born much later.

As you know, pregnancy occurs at the moment when the egg merges with the sperm inside the fallopian tube. In most cases, such an event occurs exactly on the day of ovulation or within a day after its completion. Thus, by calculating the duration of pregnancy from the moment of ovulation, it is possible to more or less accurately determine the actual period of fetal development.

However, this technique is far from always suitable for further monitoring of the course of pregnancy, since in many women ovulation does not always occur exactly in the middle of the cycle. For absolutely healthy women, this event can happen a little ahead of time or vice versa a little later. Therefore, the real (embryonic) gestational age is often simply impossible to determine.

The obstetric period began to be calculated a long time ago, when there was no information about the features of the course of pregnancy, as well as about ovulation. Many years ago, the only symptom of the onset of conception for a woman was the absence of menstruation, and therefore the period was counted from the moment of the last menstruation.

Obstetric gestational age and real calculation - the difference

The standard menstrual cycle lasts for four weeks - twenty-eight days. In this case, conception occurs somewhere on the fourteenth day, just at this time ovulation is maximally possible. Accordingly, the actual period of fetal development and obstetric will differ by about two weeks.

Accordingly, if the doctor tells you about the gestational age of four weeks, then the actual age of the embryo is only two weeks.

However, depending on individual characteristics, this difference may be greater or lesser.

If the length of your menstrual cycle is slightly different from the standard, most likely fertilization occurred a little earlier or later than the fourteenth day of the cycle. Accordingly, the actual gestational age will be slightly different than when calculating by the date of the last menstruation.

For example, if the average cycle length is not twenty-eight, but thirty-five days, then conception can occur only on the twenty-first day of the cycle, and not on the fourteenth. Accordingly, in the first week of the delay, the real period will be the third week, and by the date of the last menstruation it will be the sixth week.

When trying to correctly calculate the gestational age, you should not focus solely on the date of sexual intercourse. As practice shows, spermatozoa can remain active in the female genital tract for up to five days, waiting for the maturation of the egg and the completion of fertilization.

How else can you determine the timing?

In the very first weeks after conception, for the most accurate determination of the gestational age, you can take an analysis for hCG. The results obtained will make it possible to determine the most accurate age of the fetus.

To determine the period at a later stage of gestation, you can sign up for an ultrasound. Until the twelfth week of gestation, such a study extremely accurately shows the age of the baby, since its development is approximately the same for all women. In this case, the doctor can write as a result both the true (real) age of the fetus and the obstetric gestational age. Accordingly, it is necessary to clarify with the specialist conducting the study what exactly he has in mind.

How is the gestational age determined during a routine gynecological examination?

A qualified gynecologist, conducting a vaginal examination of the patient, can detect pregnancy at the earliest stages of development, from about the third or fourth week. But of course, the dates he named cannot be called 100% accurate.

How does the length of the cycle affect the overall duration of pregnancy?

In fact, it doesn't matter how long your monthly cycle lasts. On average, about nine months pass from the onset of conception to the date of birth, but this period may deviate in one direction or another, depending on the individual characteristics of the woman, as well as on her course of a particular pregnancy.

Conclusion

We talked with you about the difference between real and obstetric pregnancy. The correct determination of the gestational age, taking into account the length of the cycle and the approximate timing of ovulation, helps to calculate the approximate date of birth as accurately as possible. That is why it is extremely important to inform your doctor about all the features of your body.

Modern experts use generally accepted norms regarding the bearing of a fetus by a woman. An uncomplicated pregnancy lasts an average of 280 days. Usually, the very beginning of the term refers to the first day of the last menstrual bleeding. This counting system is called obstetric term. In modern gynecology, according to such data, the time of prenatal leave is calculated, the size of the fetus is estimated using ultrasound, and the estimated date of birth is calculated.

What is the obstetric week of pregnancy?

The specialist, in order to determine the time of delivery by the obstetric method, counts back exactly three months from the starting day of the last menstrual bleeding, then adds 7 days to the result. It should be borne in mind that the resulting date of birth is not an exact day, but a certain range that can deviate 10-12 days ahead or back from the most probable day of the natural birth of the fetus. Each pregnancy follows a unique scenario, so the timing of childbearing varies. It has been noticed that specialists mainly operate with the concept of an obstetric period, because almost every unexpectedly pregnant woman can name the date of the last menstruation, since it is customary to record these data on a calendar, but few people can accurately indicate the day when conception occurred.

A feature of the obstetric gestation period is that it contains a full cycle of the birth of a new life, that is, the time from the beginning of the life of the egg until the appearance of a fully developed and ready-to-live child in the outside world. There is nothing complicated about how obstetric weeks of pregnancy are considered. The week itself, as usual, is 7 days. As it was found out, the difference is hidden in the count of months. We know that the gestational age is 9 calendar months, which is equal to 10 obstetric months, which is an average of 40 weeks - if we count from the date of the last menstruation, and 38 weeks - if we start from the date of conception.

Determining the duration of pregnancy

What is the embryonic gestational age?

It is known that in medical practice, the embryonic gestational age is also calculated, which begins with the fact of conception and, as a rule, coincides with the time of ovulation. The female menstrual cycle, which lasts from the first day of menstruation until the first day of the next menstruation, is usually in the range of 28-30 days. During the first part of the cycle, the follicle matures inside the ovary; by the 14-15th day, the process of ovulation is observed, which implies the release of the formed egg from the follicle. It has been scientifically proven that after ovulation for about 2 more days, the egg retains the ability to fully develop further through fertilization. It is also taken into account that the spermatozoa produced by a man are viable and predisposed to fertilization for about 4 days. It turns out that only 6 days are distinguished by the highest probability of conception. Based on the foregoing, one can distinguish a feature of the obstetric period: it certainly exceeds the embryonic one. The difference between these concepts is 14-15 days.

Calculation of the gestational age according to ultrasound

Theoretically, it is possible to calculate the gestational age based on the size of the uterus and the nature of the movements of the fetus. These criteria cannot be considered accurate, because these are strictly individual data with a significant scatter. In fact, the fetus begins to move at 7-8 weeks of life, but the mother may feel tremors at 18-20 weeks. Every woman needs to have an idea on the topic of ovulation and the embryonic period, monitor her own menstrual cycle, and at least in general terms know how the obstetric weeks of pregnancy are considered. The availability of accurate data will facilitate medical supervision and increase the chances of a normal delivery of a healthy baby.

Today, many unenlightened people mistakenly believe that the gestational age can be determined by conducting an ultrasound examination. In reality, this is not the case. The main task of ultrasound is to assess the condition of the embryo. Experts are trying to find out what gestational age the actual size of the fetus is comparable to, based on an estimated period calculated directly from conception or the onset of the last menstrual bleeding. Ultrasound is prescribed at least 3 times to assess the dynamics of development and growth of the fetus according to the gestational age.

For example, it was previously found that the period is 32 weeks, and the ultrasound examination showed such dimensions of the fetus that are inherent only in a 29-week-old embryo. In this case, doctors will not adjust the period according to the size, but will conclude that there is a developmental delay of 3 weeks, and this implies a detailed examination and determination of the cause of the deviations.

In many cases, the pregnancy proceeds normally, and ultrasound reveals the correspondence between the size of the fetal body and the due date. This fact gives rise to a false assertion that an ultrasound examination is a way to determine the gestational age.

Based on the above information, we can conclude that it is really important for expectant mothers to know how obstetric weeks of pregnancy are considered. Experts emphasize that the correct gestational age in weeks can be established by examining a set of data, which includes the following indicators: fetal growth dynamics, the onset of the last menstrual bleeding, the results of several ultrasound examinations and the date of conception.

The doctor in the LCD talks about some obstetric weeks of pregnancy, the ultrasound sets a completely different period, and according to your calculations, the third one turns out. And how can an inexperienced future mother not get confused here. In fact, everything is not so difficult, you just need to deal with some of the nuances.

What is an obstetric period and why is it needed?

Obstetric weeks of pregnancy include the time interval from the first day of the last menstruation before pregnancy to the expected date of birth (PDR). The obstetric period is 280 days or 40 weeks, or 10 obstetric months (a month is 28 days). Obstetric weeks of pregnancy are counted already when conception has not yet occurred, but the processes of maturation and release of the egg have successfully passed.

The definition of obstetric weeks is necessary for the convenience of calculating the duration of pregnancy. After all, no doctor can say for sure when a woman ovulated and, accordingly, conception. Yes, and the woman herself can, of course, guess about the possible day of conception, but not be completely sure of it. In the meantime, almost all the fair sex remembers the date of the beginning of the last menstruation.

The embryonic period is the time of your baby's life, first in the status of an embryo, and then in the status of a fetus. The embryonic period lasts approximately 265-266 days (38 weeks or 9 normal months).

An ultrasound study determines the expected duration of pregnancy based on the size of the baby, while relying on the normative indicators of its development at embryonic (up to 12 weeks) and obstetric (after 12) weeks. The timing of the ultrasound is rather inaccurate. The size of the fetus, like the size of an adult, is individual, small children are born, heroic children are born, a slight deviation (no more than 2 weeks from the norm for the corresponding week of pregnancy) is allowed. Nevertheless, the definition is very important, a significant deviation from the normative indicators indicates various pathologies in the development of the baby.

How to count obstetric weeks of pregnancy?

The doctor should tell the future mother about what is and how the obstetric weeks of pregnancy are considered. But if suddenly he did not cope with his task, and you forgot to clarify this point with him yourself, the following information is for you.

So, how to calculate obstetric weeks of pregnancy? Everything is pretty simple. Take a calendar, remember the date of the first day of the last menstruation, count from this day (including with it) the number of days or weeks (as you wish) until today, you get. If you counted in days, do not forget to divide the resulting number by seven. If you want to know the date of the expected birth, calculate 280 days in the same way. You can determine the PDR in a different way, namely: according to the same calendar, count three months from the first day of the last menstruation back and add 7 days.

Based on the above, the difference between obstetric and fetal weeks of pregnancy is in the order in which they are counted. obstetric term is 280 days (counted from the last menstruation). While embryonic lasts about 265 days (count from the day of conception).

If the woman's menstrual cycle was regular and stable, then with a high percentage of probability it can be assumed that ovulation occurred in the middle of the cycle and in the middle of the cycle, respectively, conception occurred. That is, the difference in time between obstetric weeks of pregnancy and embryonic weeks in a healthy woman with a regular menstrual cycle lasting 28-30 days is within two weeks. In women with an irregular cycle, one can only guess about the embryonic period.

As you know, in most cases, it is quite difficult for young girls to establish the exact date of conception. That is why in medical practice, when determining the duration of pregnancy, they always started from the date of the beginning of the last menstruation preceding pregnancy. With this calculation, the so-called "obstetric" gestational age is established, which is slightly longer and differs from the real one.

Many women who become pregnant for the first time do not know what the obstetric gestational age means and how to determine it. With a normal menstrual cycle (28 days), conception is possible on about day 14. Due to the fact that the date of the last menstruation is used in the calculation, the obstetric and embryonic (real) terms of pregnancy usually do not coincide. The run-up between them is the same 2 weeks, and sometimes 3.

How to calculate the embryonic (real) gestational age?

In order for a pregnant woman to independently calculate the actual gestational age, it is necessary to know the exact date of conception. If you can’t install it, then modern ones can come to the rescue. The design of such devices is based on electronic sensors that allow you to accurately determine the gestational age. The error in this case is small.

The situation is much easier when a woman remembers exactly the date of the last sexual contact. In this case, it is necessary to calculate only how many days have passed since that moment. The resulting number of weeks will be the actual gestational age.

According to statistics, the difference between the real and obstetric period of 2 weeks is observed only in 20% of pregnant women. For another 20%, the difference between these two terms is less than 14 days. In the majority, 45%, the difference between 2 terms varies in the range of 2-3 weeks, and only in 15% of pregnant women is more than 3 weeks.

If the average duration of a woman's menstrual cycle differs from the standard 28 days, then fertilization does not occur on day 14, but a little earlier or later. Therefore, the embryonic period will differ sharply from that established by the gynecologist.

For example, if a woman's cycle lasts 35 days, then conception can only occur on day 21, and not as usual - on day 14. Therefore, the embryonic gestation period at 1 week of delay will be 5 weeks. At the same time, if you count from the last menstruation, then it will already be 6 weeks.

In the early stages of pregnancy, it is possible to determine the period accurately enough only with the help of an analysis for. With its help, the approximate age of the fetus is established. In this case, the calculation is carried out from the date of the alleged conception. More accurately allows you to set the time of ultrasound. When conducting this study, the dimensions of individual parts of the fetal body are taken into account, according to which its age is established. According to the results of the ultrasound, it can be established as an obstetric gestational age, as well as embryonic.

When determining the gestational age, you can also take into account the duration of the cycle. Indeed, with a longer menstrual cycle, conception occurs a little later, therefore, childbirth will occur later.

Thus, knowing the main differences between the obstetric and embryonic gestational age, women will share these 2 concepts, and not be surprised that the period set by the gynecologist is longer than that expected by her, which is calculated according to the date of conception.