Determination of the gestational age of the fetus
What is the gestational age of pregnancy and how is it calculated. Around these medical definitions there are many rumors and opinions. Most women consider it correct to consider the duration of pregnancy from the day of conception of the child. And it usually coincides or almost coincides with the day of ovulation. Therefore, they are genuinely surprised when they come to see a doctor and hear that they have 5 weeks instead of 3 weeks of pregnancy (1 week after the onset of the delay in menstruation)! After 5 weeks ago they just started the last menstruation, and no child was yet.
What is the reason for such an unusual calculation? With what to say exactly the date of conception is rarely what a woman can. Only my guesses. After all, not many of the planning pregnancy make folliculometry to track ovulation. And therefore, the gestational age of the embryo, and subsequently the fetus, begins to be counted from the first day of the last menstrual cycle.
Starting from this day, pregnancy is counted. And it becomes clear what the "approximate date of the beginning of the gestational period" means - the first day of the last menstruation, the menstrual cycle, when the conception occurred. To find out the date of birth, the doctor adds 280 days. A full-term child is considered on time from the 260th day. That is, from 37 weeks of pregnancy. Perezrelym if more than 294 days have passed since the last menstruation.
So the gestational or obstetric term of pregnancy doctors put when a woman came to see them for the first time, when registering. And in the future this term is being specified. Based on ultrasound data. The most accurate is ultrasound in the first trimester of pregnancy. The longer the gestation period, the less accurate is the determination of the length of pregnancy by ultrasound, as the fetal size in women varies greatly, depends on external factors and is genetically programmed. It is also taken into account, especially at the first pregnancy, the date of the beginning of fetal movements. Further, the definition of the period depends on the doctor. Someone considers the main point of reference - the first day of menstruation, someone is guided by the first ultrasound, and some calculate the average time, based on the available data. This is especially true in the case when a woman can not name the exact date of the last menstruation.
Determination of the gestational age of the fetus по УЗИ
The fetal egg on good apparatus for ultrasound examination can be seen in the uterus even before the onset of menstruation, with a 28-day cycle around the 25th day, that is, 10 days after ovulation and conception. On the 6th day of menstruation, an embryo is already visible. And on the 10th day his heart contractions are fixed. But with a longer menstrual cycle and a technique of low level, there may be small errors.
Approximately 2 weeks after conception, an expert in ultrasound diagnostics can quite accurately put the gestation period for KTP - the coccyx-parietal fetal size. To find out the gestational period of the fetus, more precisely the embryo and calculate the expected date of birth according to the size of only the fetal egg (when the embryo is not yet visible) will not work. The embryo grows about 1 mm per day. The accuracy of determining the date of birth under this information is plus or minus three days. And this is much higher than the usual calculations for the menstrual cycle.
Is it worth it to know the exact gestational period, to undergo ultrasound in the first trimester of pregnancy? The standard recommendation is ultrasound at 12-13 weeks, the so-called first screening, when the doctor can fairly accurately assess the risk of the probability of chromosomal pathology in the fetus. But often there is a need for an earlier passage of ultrasound. For example, if there is no certainty that the pregnancy is developing and that it is a uterus. Ultrasound is safe at any time of pregnancy and does not provoke malformations in the child, does not cause miscarriage. Nevertheless, it is better not to do ultrasound "for yourself", but first go to the gynecologist and find out whether you need to conduct this research right now for you, at this pregnancy and in this situation.
How to calculate gestational gestation after 12-13 weeks, when CTE becomes uninformative due to changes in the position of the fetal head? Then the indicator of BDP - biparietal size of the fetal head becomes informative. Some specialists calculate the ratio of the BDP and the length of the femur of the child for the accuracy of the determination.
An enlarged or reduced fetal head may speak of brain developmental defects, fetal development retardation. Actually, it is because of the second reason that it is so important to know the exact gestational age, according to the ktg and the accompanying examinations it will not be recognized. Also, knowing the exact age of the fetus, the doctors become aware of the date in which this fruit will already be mature, full-term. This is also important. Especially in high-risk pregnancies. For example, with severe gestosis, when a woman expects a cesarean section. The error in determining the duration of pregnancy for BDP is no more than 7 days.
In addition to the results of ultrasound, a gynecologist can take into account the fact that when the expectant mother started to feel the fetus moving. Usually in the case of primipara this is 20 weeks. That is, the birth should begin about 20 weeks after this date. If the woman is a rabbits, then after 22 weeks. Although, in practice, many women begin to feel a child before the "deadline".
The gestation period or gestational age of the fetus is the indicators that can be known to the accuracy of the day, except in artificial insemination, when the day of embryo implantation into the uterus is known. Still other methods have small errors. But do not bother with this topic. Trust in this question to the doctor. And it is quite enough to remember the date of the beginning of your last menstruation.