With the onset of a long-awaited pregnancy, a woman wonders when will a baby be born? There are several ways to calculate the date of birth, but it is better to do this with your doctor, and not on your own.
How to determine the date of birth by menstruation and ovulation?
Pregnancy occurs when the ovum leaves the ovary, but the woman cannot know exactly when the ovulation occurred, only if she did not track the mature egg in order to become pregnant.
So, it is tentatively accepted that this event occurs on day 14 (with a cycle of 28 days). According to obstetric estimates, a pregnancy lasts 280 days, that is how much you need to add to the date of ovulation in order to find out the approximate term of birth.
To calculate the date of delivery for menstruation, there is a simple Negele formula: it is necessary to subtract three months from the date of the last menstruation, and then add seven days. Of course, this calculation is approximate, because it is suitable for those who have a cycle of 28 days, in another case, the date of delivery can move forward or backward for a few days.
How to determine the date of birth by ultrasound?
To determine the day of birth, an ultrasound scan is best done before 12 weeks of pregnancy. At this time, you can determine the size of the fetus more accurately. To the existing period it is necessary to add the missing up to forty weeks. At a later time, in every woman, the fetus gains weight at its own pace, it depends on the individual characteristics of the body and possible diseases that the woman has. Therefore, in the conclusion of an ultrasound scan (second and third trimester), the gestational age is indicated with an error of 1-2 weeks.
How to determine the date of birth by gynecological and obstetric examination?
According to the size of the uterus, during examination for up to 12 weeks, a gynecologist with great experience can determine which week of pregnancy a woman is. After which you can add the remaining weeks, then you get the date of delivery. At a later time, an increase in the fetus, and, consequently, the uterus, occurs individually for everyone, so this method becomes unreliable.
Of course, in the second half of pregnancy, you can use obstetric examination, that is, determine the height of the uterine fundus, and measure the girth of the abdomen at the navel. For each term, there are indicators, knowing what week the woman is pregnant, you can determine the date of birth by adding the remaining term. An incorrect measurement or pathology, for example, water shortage or polyhydramnios, when the volume of the abdomen does not correspond to the available period, can distort the data.
How to determine the date of birth by moving the fetus?
It is generally accepted that women with their first pregnancy begin to feel the fetus for a period of twenty weeks, and multiparous - for a period of eighteen weeks. Accordingly, adding twenty and twenty-two weeks to the date when the first stirring was noticed, we can calculate the day of birth. This method cannot be considered reliable, as thin women can feel movements much earlier (from sixteen weeks), and full ones later (at twenty - twenty two weeks). This is a variant of the norm, but greatly distorts the calculation of the date of birth.
You should try to make calculations in all possible ways, since correctly calculating the date of birth will not work out by the method alone. It is worth considering that a normal pregnancy can last not only exactly forty weeks, but also less (thirty-eight) and more (forty-two). Therefore, any calculation will be approximate. The most commonly used are calculations for menstruation and ultrasound. Do not expect too much the appearance of the baby on a particular day, since normal childbirth will begin when the cervix and the fetus are fully ripe.