Date of birth: how to calculate the most accurate date of birth?

The date of birth, this question arises in every woman after the confirmation of pregnancy. A woman is overwhelmed with a feeling of happiness. She calculates when approximately the day of the arrival of her baby will come and she will hold him in her arms. In the article you will read in which ways you can calculate the expected date of birth.

Date of childbirth: How to calculate it?

The exact date of childbirth can not be determined, only approximate. Only 1 in 20 mothers give birth on the day of calculated childbirth. It is most accurately calculated during regular menstruation.

It is assumed that fertilization occurred on the 14th day from the first day of menstruation. Therefore, ovulation should occur on this day.

The normal length of pregnancy lasts from the 38th to the 40th week, which is 267-290 days. As a rule, the birth of a premature newborn occurs 2 weeks before or 2 weeks after the calculated date of birth. But each pregnancy and newborn develops a little differently.

How can I calculate the most accurate date of birth?

Can it be calculated at all? And how? We know several ways...

According to the day of fertilization

If a woman knows the exact day of fertilization, according to it, it is possible to calculate a fairly approximate date of birth. With a regular menstrual cycle, ovulation occurs on about the 14th day.

The sperm in the uterus retains its fertilizing ability for 3 days. The egg is able to be fertilized for approximately 24 hours.

So, fertilizing coitus occurs between the 11th and 15th day of the cycle. The due date is most likely to occur in 38 weeks or 267 days.

Naegele's rule

The Naegele rule calculation is based on a 28-day regular menstrual cycle. Add one year, 7 days to the 1st day of the last menstrual period and subtract 3 calendar months.

Your gynaecologist will calculate your probable due date using a device called a gravidometer. The gravidometer is based on the Naegele rule.

When is my due date?

If a woman doesn't have a regular 28-day cycle, you need to either add or subtract days.

For example, with a 35-day cycle, add 1 year, minus 3 months, and add 7 + 7 = 14 days.
With the 7 days, we are working purely mathematically.
35-day cycle minus 28-day cycle (35-28) = 7 days difference, so the 7 days are added to the plus.

With a 21 day cycle, 7 days must be subtracted. 21 days - 28 days = - 7 days.

According to the fetal movements

The date calculated according to the first fetal movements is only a guideline date. A first-time mother is likely to feel the first fetal movements at week 20. 20 weeks should be added to this date. In a multiparous mother, the first movements come at week 18, so add 22 weeks.

But this calculation is not very reliable.

According to the ultrasound.

The size of the fetus of the first ultrasound examination is also a parameter to the calculated date of birth.

But the most accurate is considered to be the sonographic examination in the first trimester, between the 11th and 14th week of pregnancy. It measures the CRL of the fetus.

CRL = fetal length from the vertex to the coccyx.

If the date calculated by the ultrasound differs from the calculated date by more than a week, the date is adjusted according to the CRL measured by the ultrasound.

You can read more about sonographic calculation of the due date according to fetal length in the article.

Date of delivery after IVF (Intrauterine Insemination)

With IVF, we know the exact day the embryo is inserted into the uterus. After the embryo is inserted, the clinic will tell you exactly how old the embryo is. Most often, a 5-day embryo is inserted. So you can calculate the most accurate date by adding 38 weeks and subtracting 5 days.

IVF = in vitro fertilization, the fertilization of an egg outside the woman's body.

You can read more about the length of pregnancy in the article How long does pregnancy last? How many days, weeks and months?