Why is the term for ultrasound less than obstetric. Why is the term for ultrasound longer than for menstruation? Real time carrying a baby

A woman who finds herself in a position in most cases is interested in the question of which of the two is true: the period for menstruation or the period for ultrasound. And if experienced women do not experience problems with determining the age of the fetus, then for the first time pregnant women do not have a clear idea about the differences between obstetric and gestational periods.

When diagnosing pregnancy, the gynecologist voices the obstetric period in weeks. An important feature is that the reporting point is the first day of the menstrual cycle. As you know, conception occurs during the period of ovulation (about day 14). In this scenario, in fact, the woman is not yet pregnant at the moment when menstruation begins. That is why, in most cases, the approximate date of birth (DDR) differs by 2 weeks from the real one or the one set by ultrasound in a smaller direction.

But it is this method that is optimal and is used in obstetric practice. This is true, because the egg begins its development on the first day of menstruation, and then matures and is fertilized, and if not, it dies. Therefore, the obstetric period can be considered the "age" of the egg. Also, menstrual cycles are individual and can vary greatly from woman to woman. Although the 28-day menstrual cycle is considered to be a reference, the actual values can vary greatly.

0dV8PW_Yll8

So, many women may have a cycle of more than 28 days, for example, 35. In this case, ovulation occurs on his 16-17th day. Accordingly, if the cycle is less, for example, 21 days, then the release of the egg from the body of the ovary takes place on the 10-11th day. To simplify the work of specialists, it is customary to consider the beginning of pregnancy from the first day of the last menstruation, which is called the obstetric period.

According to the results of ultrasound examination

In the case of determining the maturity of the fetus according to the results of an ultrasound examination, a controversial situation may arise:

The temporary course of pregnancy by ultrasound is determined by assessing the development of the fetus, metric indicators, the condition of the uterus and the placental barrier (in the II and III trimesters). One of the indicators is KTP (coccygeal-parietal size), which is almost the same for different fruits on early stages development. Pay attention to the size of the fetal egg in the first 12 weeks of gestation. The most accurate is the number of weeks established by ultrasound in the first trimester of pregnancy (up to 12 weeks). After the indicators may vary up or down due to the individual characteristics of the development of the unborn child.
As a rule, the embryonic period determined by ultrasound indicates the period from the moment of fertilization of the egg by male material to the present, therefore it is considered to be true in fact. Most often there are discrepancies of about 2 weeks between the EDD by ultrasound or calculated by monthly. But disability certificates and other documents are issued based on the obstetric age of the fetus, which is indicated in the mother's passport and documentation in the antenatal clinic.

HAPm0O1ujjw

Conclusion and Conclusions

Be that as it may, it is almost impossible to establish exactly when the child was conceived and when he will be born. Even knowing the exact date of the “decisive” sexual intercourse, one cannot be sure that fertilization took place on that day, since spermatozoa can exist for 24 hours. Moreover, there are many factors that provoke labor activity earlier than expected.

If we consider the question of the correctness of the period for menstruation or ultrasound, it should be said that both are correct, but traditionally obstetricians focus on the first option. This avoids confusion in the future and considers a possible delivery on the indicated dates. But, according to statistics, not every woman gives birth on the day established by specialists. It is considered normal to have a run of 4 weeks (from 38 to 42 weeks of gestation, respectively).

The gestational age is an important parameter on the basis of which the growth and development of the fetus is analyzed, and the expected date of birth is also calculated. The difference in numbers can lead to bewilderment and confusion for both expectant mothers and doctors. It is possible to determine the gestational age according to various parameters: the results of an ultrasound examination, the size of the uterus during a vaginal examination, movement, but most often the main reference point is menstruation. What does it mean if these numbers do not match, for example, the period for ultrasound is longer than for menstruation? When should a expectant mother worry? Can a doctor make a mistake and how to calculate correctly?

Read in this article

Causes of differences in obstetric terms and monthly

For a more thorough understanding, it is necessary to understand on the basis of what parameters it is possible to determine the gestational age.

The most significant guide for which you need to know the first day of the onset of the last spotting. If a woman remembers this date exactly, then in all situations this parameter is preferred.
The gestational age can also be determined by ultrasound examination (ultrasound) of the fetus. For the entire period of gestation, a woman performs it at least three times. The most informative for the setting of the term is an ultrasound examination at 11-13 weeks. The main measured parameter is KTR (the distance from the coccyx to the crown of the embryo). Age is determined by its value in weeks. Sometimes ultrasound is performed at a very short time, when visualization of even the embryo itself is difficult, and only the fetal egg is determined. It happens that some “not sharpened” devices for obstetrics can give out a period from the moment of ovulation. In such a situation, of course, the period for menstruation and ultrasound does not coincide. The difference will be on average 2-3 weeks. As a rule, obstetrician-gynecologists are aware of such nuances of research, and take this into account when determining the number of weeks of pregnancy.
An important parameter is the determination of the degree of enlargement of the uterus during the initial examination of a woman by a gynecologist. Experienced doctors can tell the time to within a few days. But with each month of pregnancy, the error in setting the term increases. The most informative such study is from 7 to 16 weeks.
Also, the gestational age can be determined by the beginning of fetal movements. On average, a woman feels the beginning of movements during her first pregnancy at 20 - 22 weeks, with a second - at 18 - 20. But future baby begins to move actively from the second month. Therefore, very often women note that even at 14-16 weeks they distinguish the movement of their crumbs. That's why this study gives a very approximate and subjective result. In such situations, there may also be a discrepancy in the gestational age.

It becomes clear that you have to take into account all the nuances and determine the number of weeks of gestation by all possible methods. With significant deviations, the average period is displayed with an emphasis on the indicator for menstruation or ultrasound. Why might there be differences? Consider the most popular situations when the numbers will differ.

Short or long menstrual cycle

Conception occurs during ovulation, usually on the 14th - 16th day. In women whose cycle length is more or less than the standard 28 days, the release of the egg from the ovary is shifted. Ovulation can occur at the beginning (even on the 3rd - 5th day of critical days) or on the eve of menstruation. Accordingly, the absence of a pattern leads to the fact that the gestational age in terms of the size of the fetus (this is determined by ultrasound) may not correspond to similar figures for menstruation. But, as a rule, such a run is no more than 2 - 3 weeks and can be traced throughout the pregnancy.

With a short or long cycle, often for menstruation, women take on the most early dates. The discharge, of course, differs from ordinary menstruation in the number of days and profusion, but this is not always noticed.

irregular periods

Often, the period for ultrasound is less than for menstruation, if the woman’s cycle is completely irregular, and the interval between critical days is more than 35 days. This happens with PCOS (polycystic ovary syndrome), endocrine diseases, with pathology of the pituitary gland and hypothalamus, etc. If the pregnancy is planned, then the girl can purposefully “catch” ovulation, which is not so easy to do in such a situation. The most convenient way is to build a graph, in addition to which you can determine the release of an egg from the ovary. If the doctor knows the approximate date of ovulation, then it will be easier to compare all the dates and derive the most accurate one.

Loop failure

Pregnancy is also possible against the background. This can be either a single failure due to external factors, or induced, for example, while taking hormonal contraceptives. Girls using emergency contraception, for example, or, believe that unprotected sex immediately after taking the pills will also not lead to pregnancy. In fact, these hormonal drugs only prevent the possible conception that could have happened within 48 to 72 hours before taking the remedy.

Failure to follow the rules for taking oral contraceptives - skipping a pill, changing the time - can lead to a failure of the menstrual cycle and pregnancy. In such a situation, there is also often a difference in the period for menstruation, ultrasound and other parameters.

Cycle failure can occur against the background of stress and psycho-emotional experiences, as well as with an increase in body weight. If conception occurs just for such a period, then differences in the established dates may be observed.

Lactation

During breastfeeding, especially during the first year, the process of releasing an egg may not exactly match the cyclical nature of the menstrual cycle. As a result, when calculating the period by monthly, a big error is made in terms, sometimes up to 3-4 weeks.

Intrauterine interventions

Any manipulation, accompanied by penetration into the uterine cavity, can cause a violation of the menstrual cycle. Also, after them, for another month or two, irregular spotting is often observed, which a woman can falsely take for menstruation. This can happen after diagnostic curettage, hysteroscopy, abortion (including medication), etc.

When using assistive techniques for conception

Often you have to resort to ovulation stimulation in a woman, the creation of an artificial hormonal background for conception to occur. In such cases, there may also be a difference between ultrasound and menstruation. Especially if IVF (in vitro fertilization) was used. AT similar situations it is difficult for women to figure out the timing on their own, since first the eggs are taken, which are fertilized outside the woman's body. And only after that, on the 21st day of the cycle, the embryos are replanted. As a rule, the difference in terms for ultrasound and menstruation will be the same for all studies, for example, at two or three weeks.

If there was a threat of interruption in the early term

Early pregnancy can be accompanied by a variety of spotting, which a woman can take for menstruation. In fact, these are the first symptoms of an interrupt threat. This can last up to two to three months, during which on the expected critical days bloody daub or even moderate discharge will appear. In such situations, the difference in the figures of the period between the monthly and data obtained by other methods will be immediately interpreted correctly with a thorough history taking.

Development of a large fetus

In the case of the development of a large fetus in utero, a false impression is created that pregnancy by ultrasound is greater than by menstruation. However, such a difference will be visible starting from 20 to 22 weeks. Often only certain parameters of the baby are ahead, for example, the circumference of the abdomen or the length of the femur. At 11 - 13 weeks, the gestational age according to ultrasound should correspond to others.

Permissible difference

Determining the term is important not only for determining the expected date of birth (PDR), but also for assessing the growth rate of the baby in utero. For example, a developmental delay of more than 4 to 6 weeks is an indication for emergency delivery at any time during gestation.

A delay of up to two weeks is acceptable. It is also not critical if the difference can be traced from the very beginning of pregnancy. This indicates that errors were initially made in the definition.

If the period for ultrasound exceeds the period for menstruation, this has a more favorable prognosis than the reverse situation. In case of lagging, you should make sure that the fetus does not suffer in utero, it has enough nutrients and oxygen, and the placenta functions in full.

How long to focus on childbirth

Both doctors and women often face the question of how to determine pdr - by ultrasound or by menstruation. The approach is individual in each situation.

If a future mom clearly remembers the date of the last menstruation, her cycle is regular and there have been no special changes in her lifestyle lately, then menstruation is preferred.

In a situation where a woman hardly remembers the last critical days, or her cycle is irregular, its duration is more than 35 days, then you should be guided by the ultrasound of the fetus. Moreover, all the dates of its implementation are taken into account, compared, and only after that the estimated date of delivery is determined.

Why are weeks of pregnancy counted?

Everyone knows that the duration of pregnancy is nine months. However, this is a very average figure. For a more thorough monitoring of a woman "in position", for monitoring the growth and development of the fetus, terms in weeks and days are used. So, full-term pregnancy is considered from 37 to 42 weeks of gestation, which ranges from 259 to 294 days. A child born in this interval has completely adapted organ systems for life in the Earth's atmosphere (of course, if the baby does not have a congenital pathology or infection).

Here's why you need to know the exact gestational age:

Timely identify the pathology at the rate of maturation of the baby and carry out the necessary treatment. Sometimes it is even premature delivery, when the continued presence of the baby in utero has a high risk for his life.
To systematize the clinical examination of pregnant women and the timing of registration. The results are evaluated possible complications measures are being taken to prevent them.
Knowing the gestational age, you can set the deadline for the expected date of birth. Overwearing can adversely affect the health of the baby, in which case labor can be induced.

Is the time determined by ultrasound accurate?

During pregnancy, ultrasound is performed several times. What timeframe is more accurate? First of all, the results of ultrasound obtained from the 11th to the 13th week, inclusive, should be adopted. It is during this period that the size of the crumbs is such that it is possible to accurately determine the reference points for measurement (as a rule, this is the KTP - the distance from the coccyx to the top of the parietal bone on the head of the embryo), which can be displayed on the screen at once.

In the short term, the parameters are approximate, since often only the fetal egg is visible or the structures of the unborn baby are not clearly distinguishable.

After 16 - 18 weeks, only individual parts of the fetus can be displayed on the monitor - the head, arm, leg or tummy. These structures are measured and the approximate gestational age is determined from the summary tables. The longer the period, the less indicative the numbers are, since there is still someone thin in the mother’s stomach, while others have chubby cheeks and legs.

Determining the gestational age has an important diagnostic and prognostic value for the successful management of a woman during childbearing and preparing her for childbirth. That is why every girl should strictly maintain a menstrual calendar and mark in it all significant health events. This is great help doctors, help in solving emerging problems. Of course, it doesn’t matter whether they gave birth by ultrasound or by menstruation, the main thing is that mom and baby are healthy and nothing threatens their lives. And this can only be achieved through coordinated work between doctors and women.

Dear Olya!

Your assumption that the obstetric gestational age is determined by ultrasound is not entirely correct. This study is more likely not to establish the term, but to determine whether the size of the fetus corresponds to the estimated true gestational age.

Calculation of the gestational age on ultrasound

During an ultrasound examination in the early stages, fetal development indicators are evaluated according to tables calculated for the embryonic period, which is 2 weeks less than obstetric. There are several such tables compiled by different authors, which contain data on the average size of the fetus at different stages of pregnancy and suggest an error interval that can reach 2 weeks. Ultrasound machines have built-in programs in which averaged indicators taken from different tables are taken. It is possible to judge whether the fetus has a developmental delay only if the woman knows exactly when the conception occurred, otherwise the specialist can only make a preliminary conclusion, which must be confirmed by additional studies.

In the early stages of pregnancy (up to 12 weeks), experts pay attention to the length of the embryo from the coccyx to the crown (KTP) and the average internal diameter of the fetal egg. At later stages of pregnancy, the development of the fetus occurs in jumps, so the tables that the ultrasound doctor is guided by are designed for the obstetric period, that is, from the first day of the last menstruation.

It is for this reason that there are often discrepancies between the deadline set for ultrasound and the deadline that passes in all the documentation drawn up in the antenatal clinic. Therefore, very often ultrasound doctors give out some average result, taking into account the data on the date of the last menstruation, the date of conception, the results of previous ultrasounds and data on the development and growth of the fetus, which in most cases coincides with the true gestational age if it proceeds normally.

How to determine the date of conception?

To determine the date of conception, you need to calculate the timing at which you ovulated and analyze which of the days when you had sexual intimacy was closest to the period of ovulation. It is worth noting that it is almost impossible to determine exactly when a child was conceived, but, nevertheless, an approximate calculation can be made.

To determine when you ovulate, you need to know the length of your menstrual cycle. If it is stable and is 28 days, then ovulation most likely occurs on the 14th day of m.c. If its duration is 29 days, then on the 15th day of the m.c. With a 30-day cycle on day 16, etc. The data from the first ultrasound and the level of hCG according to the analysis from 7.04 indicate that you could have ovulated between March 6 and March 8, 2015. If you adhere to these data, then according to the results of subsequent ultrasound, the development of the child approximately corresponds to the embryonic gestational age with a slight excess. But, as mentioned earlier, fetal development is spasmodic, so an error of +/- 2 weeks is considered a variant of the norm.

The diagnosis of "fetal growth retardation" cannot be made solely on the basis of a difference in gestational age. Slow fetal development must be confirmed by regular measurements of the height of the fundus of the uterus and the circumference of the abdomen, which are made at each visit to the obstetrician-gynecologist; study of the level of placental hormones; CTG data (fetal cardiac cardiotocography); and ultrasound in case of delayed development reveals a low birth weight of the fetus, disproportionate growth of organs, impaired blood circulation through the vessels of the umbilical cord and arteries, and other possible deviations from the norm.

Best regards, Xenia

The duration of pregnancy is a significant indicator. It evaluates how the fetus develops, finds out the expected date of birth. There are many ways in which a pregnant woman can determine the period (for example, by the date of the last menstruation that began, by ovulation).

Ultrasound diagnostics (USD) deserves special attention. It is prescribed during the period of gestation for several reasons. First of all, ultrasound is necessary to confirm the development of uterine pregnancy. Among the reasons for performing a scan is the determination of the duration of the gestation period.

Features of setting a deadline

With the help of ultrasound diagnostics, the duration of the gestation period can be determined as accurately as possible in the first trimester. In the following trimesters, the information received is not entirely correct. Errors arise due to the constitutional features of the development of the fetus, as well as due to existing and progressive complications in some women during pregnancy.

How is the duration of gestation determined using ultrasound?

In the first 3 months, when it is impossible to see the embryo, specialists will find out the term by ultrasound according to the calculated SVD of the fetal egg - the average inner diameter. This parameter is determined by the algorithm below:

the measurement of the anteroposterior and longitudinal dimensions of the fetal egg is carried out during longitudinal scanning;
width measurement is performed during transverse scanning;
the arithmetic mean is calculated from the obtained numbers.

At 5.5 weeks for the average internal diameter, values from 0.6 to 0.7 cm are characteristic. Every day the embryo grows with a normally developing pregnancy:

at 6 weeks the indicator under consideration already becomes equal to 1.1 cm;
at 6.5 weeks - 1.4 cm;
at 7 weeks - 1.9 cm;
at 7.5 weeks - 2.3 cm;
at 8 weeks - 2.7 cm.

When the embryo begins to be visualized, the KTP becomes an indicator that allows you to find out the duration of the gestation period - a size called the coccyx-parietal.

Determination of KTP with ultrasound

It is determined by sagittal scanning. This parameter means the maximum distance from the coccyx to the outer contour of the head end:

at 1 month and 3 weeks. CTE is 0.81 cm;
at 2 months - 1.48 cm;
at 2 months and 1 week. - 2.24 cm;
at 2 months and 2 weeks. - 3.12 cm;
at 2 months and 3 weeks. - 4.21 cm;
at 3 months - 5.11 cm;
at 3 months and 1 week. - 6.32 cm;
at 3 months and 2 weeks. - 7.67 cm.

In the II and next trimesters, the duration of pregnancy is determined by various fetometric indicators.

Specialists can take into account the size of the fetal head in circumference, biparietal size, the average diameters of the abdomen and chest, the size of the abdomen in circumference, the femur in length.

What period does ultrasound show: obstetric or from the moment of conception?

Obstetrician-gynecologists use terms such as obstetric and gestational (embryonic) terms of pregnancy in their work. There is a slight difference between these concepts. The obstetric term refers to the number of weeks that have passed since the beginning of the last menstruation. The gestational (embryonic) term is the period that begins from the moment of fertilization of the egg.

The period determined by ultrasound is considered embryonic. In obstetric practice, the first concept is widely used. That is why, in order to avoid confusion, experts translate the gestational period into obstetric, adding 2 weeks to it.

If the period calculated according to the ultrasound data exceeds the obstetric ...

Theoretically, the gestational period is a couple of weeks less than the obstetric one. However, sometimes ultrasound diagnostics show something completely different. Some women note that their gestational age according to ultrasound is longer than obstetric. This is a perfectly acceptable occurrence.

The difference is explained by a decrease in the accuracy of determining the period as the fetus develops. The most accurate information is provided by an ultrasound scan performed in the first 3 months of pregnancy. During this period, all women develop the fetus almost the same way, so the errors in determining the term are minimal.

In the II trimester, the gestational age can be quite accurately determined by fetometric parameters, but in the III trimester errors already occur due to the fact that each fetus begins to develop individually, genetic factors influence. Errors in some cases are ± 3-4 weeks. In the last trimester of pregnancy, fetometry is recommended not to specify the duration of gestation, but to determine whether the size of the fetus corresponds to an already known period.

Why is the term specified with the help of ultrasound?

Post-term pregnancy is one of the problems faced by women in the position. In this condition, the embryonic and obstetric period is greater than the established values. Normal pregnancy lasts 38 embryonic or 40 obstetric weeks. Postterm pregnancy is referred to as factors that increase the likelihood of complications during delivery and lead to an increase in perinatal morbidity and mortality.

To prevent the consequences of a post-term pregnancy, there are certain preventive measures. One of them is the exact determination of the gestational age based on the results of ultrasound diagnostics (it is desirable that women who are in position are scanned no later than 20 weeks). Determining the number of weeks also avoids unnecessary induction of labor.

Knowing the duration of the gestation period allows the doctor to determine whether the fetus is developing according to the norm, whether there are any deviations. Another reason why you need to know the exact number of weeks is the need for a woman to undergo screenings, take various tests at a certain time (if you take this or that test later or earlier, you can get an unreliable result).

In conclusion, it is worth noting that ultrasound scanning is a fairly simple way to determine the gestational age. The method gives the most accurate information in the first trimester. It is from the period calculated at the beginning of pregnancy that doctors start in the future. It is also worth noting that many mothers are interested in the safety of ultrasound. Ultrasonic waves can be harmful. However, modern devices have a minimal effect on the body, so the diagnostic method is considered safe for both the expectant mother and the fetus.