As soon as a woman finds out about pregnancy, one of her main questions and questions of her relatives addressed to her becomes: “When to give birth?”. Of course, in order to determine the date of birth, it is important to understand at what stage of pregnancy the expectant mother is at the moment. How to calculate the gestational age?
Special period
Everyone knows that pregnancy lasts 9 months, but this figure is approximate. It will not be possible to accurately determine the date of birth, accurate to the week, if only because a living organism is not a mechanism, but something more complex and individual. Pregnancy is an amazing time when, from the very moment of conception, a separate person develops in the mother’s body with her DNA and blood group, which may differ from the mother. In the placenta, which is a barrier between the mother and the fetus, there are two layers - the maternal and the fetal. Maternal blood and fetal blood do not mix, but exchange substances - from the mother the baby receives nutrients, and waste products are removed from the fetus. One can only imagine how complicated the development process is from one fertilized cell and the whole human body with all systems of organs and tissues, the most complicated brain! Of course, the timing of this development may fluctuate and does not necessarily fit into the expected figure. Much more indicative will be the maturity of the child’s body and the processes in the mother’s body that indicate readiness for childbirth.
Many children are born 1-2 weeks earlier than expected. This is normal and does not affect their health in any way - by this time they are already considered full-term and usually have height and weight within normal limits.
Obstetric and True Pregnancy
Pregnancy is determined in two ways. As you know, pregnancy begins at the time of conception, i.e. fertilization of the egg. In 80% of cases, 266 days elapse from this moment to childbirth, i.e. 38 weeks. This is the true gestational age. However, not all women know the date of conception. Especially if the sex life is regular, but menstruation is not very, so it’s difficult to say exactly in which period ovulation occurred.
Another way to determine the gestational age comes to the rescue - obstetric. It allows you to calculate the gestational age for the last monthly. It is noted that from the beginning of the last menstrual period until delivery, 280 days usually pass, in other words, 40 weeks. Therefore, the start date of menstruation is considered the start date of pregnancy, although objectively conception will occur after about 2 weeks from this day.
How to determine the date of delivery?
As already mentioned, you can add to the start date of the last monthly 40 weeks. It is most convenient to calculate the gestational age in weeks according to the calendar. There is also the Negel method. It proposes to move on the calendar not forward, but backward, because years are cyclical. It is enough to subtract 3 months from the date of the monthly and add a week. These are all known ways to calculate the period of pregnancy by menstruation.
Ultrasound scan
If your period is irregular, and you are not sure that you remember the date of the last menstruation, an ultrasound will help you to determine the period. True, this method is most accurate in the very early stages of pregnancy, up to about 7 weeks. At this time, all embryos develop equally. Later, the development of each small organism goes at its own pace, so the determination of the term will be only approximate. The longer the gestation period, the more difficult it is to determine the date of conception.
Uterine size
A gynecologist can determine the date of conception only at the very beginning of pregnancy. But starting from the 2nd trimester, the doctor can feel the uterus and determine its length. With each week, it increases by 1 cm, which will tell the doctor how to calculate the gestational age. But these calculations, too, will not be guaranteed accurate.
The location of the uterus relative to the pubic bones and the navel also changes with increasing time. At 12 weeks, the uterus is located in the upper part of the womb. At 16 weeks, its bottom is between the navel and the womb. At week 20, the organ is approaching the navel in its position, but has not yet reached it. And at 24 weeks the uterus already reaches the navel. At week 28, the bottom of the uterus is 2 fingers above the navel. At 32 weeks, it is located between the xiphoid process of the sternum and the navel. At 36 weeks, the uterus abuts against the ribs from below. The navel is smoothed. In this position, the organ can compress the lungs and organs of the abdominal cavity, in this period the woman experiences maximum discomfort. The circumference of the abdomen usually reaches 90 cm.
At 40 weeks, the stomach falls a little down. The baby is already ready to be born, and the uterus is also preparing for this event. Therefore, the bottom of the uterus is again between the xiphoid process and the navel. The navel protrudes, and the circumference of the abdomen becomes even larger. On average - 95-98 cm.
Calendar method
This method consists in measuring basal temperature daily. It is measured in the morning in the rectum at the same time. Data is recorded in graph form. The lowest temperature drop will indicate ovulation, followed by a sharp rise. This method is also used for protection. However, if there is a goal to get pregnant, a woman monitors the date of ovulation with a completely different purpose. The date of conception will tell you how to calculate the gestational age. We can conditionally relate to the calendar method the situation when the sex life is irregular, so you can accurately tell the date of a possible conception.
HCG analysis
This analysis is used to determine the presence of pregnancy and identify pathologies in the embryo. Approximately the level of this hormone at the beginning of pregnancy can determine the term. This method does not differ in accuracy.
First stir
Another very approximate guideline for determining the term is the movement of the fetus. Women who are pregnant for the first time usually feel it at 20 weeks. In the second and third pregnancy, this can be felt earlier. Usually at 18 weeks. These movements of the child are very weak, to some they resemble gurgling, to someone stroking or tickling. Sometimes women can confuse intestinal motility with them, because during pregnancy, its work changes and gas formation intensifies. For about 24 weeks, these movements are more distinct and resemble tremors. Moreover, other people who put a hand on their stomach can feel them through the abdominal wall. You can try to calculate the gestational age both by fetal movements and by other signs, but you should not count on the reliability of these results. Although before, when medicine did not yet know many diagnostic methods, the term was usually determined by the movement of the fetus.
Belly size
An obstetrician-gynecologist does not just like that at each visit measures the patient’s stomach. By increasing it, one can judge the term of future birth. However, it is important to consider the complexion and weight of the woman.
What to trust?
How to calculate the exact gestational age? Your calculation will be most accurate if you know the date of conception. Then you can accurately determine the gestational age in weeks. But the date of birth you can determine only approximately. During pregnancy, together with the doctor, this estimated date will be adjusted. Closer to this event, the processes in your body will signal readiness for childbirth.
The most accurate calculation of the gestational age in weeks, as you know, allows a doctor’s consultation, which will take into account the date of the last menstruation or the exact date of conception, and ultrasound data, and the size of the abdomen, and the height of the uterus. Together, all factors can give a reliable result. But counting on the fact that you will accurately predict the date of birth up to a day is not worth it. The element of unpredictability always remains, and be prepared for the baby to appear 1-2 weeks earlier or later.
How to calculate the gestational age yourself? In order not to lose count, there are pregnancy calculators, which, by the date of the onset of menstruation, allow you to calculate both the period at the moment and the date of the expected birth. And yet, all pregnant women attend a antenatal clinic, so clarify this issue with an obstetrician-gynecologist.