Calculate the date of delivery: with these formulas

Even at the beginning of pregnancy, you can calculate the delivery date yourself using a simple formula. We show you how to do this in this article.

Pregnancy - how to calculate the date of delivery

If you know the day of conception, for example with an artificial insemination, the calculation of the date of birth is very simple.

In this case, simply add 38 weeks to the fertilization date.
If it is not an artificial insemination, but you know when you have had intercourse and that you became pregnant, there is little need to change the formula.
It can take up to three days between sexual intercourse and fertilization of the egg by a sperm. So add two more days to the 38 weeks to determine the date of delivery.
However, the so-called “Nägele formula” is used much more frequently to calculate the delivery date.
To do this, you need to know when you last had your menstrual period. Take the first day of your last menstrual period and add seven days to it.
Subtract three months from this date and add one year. The date calculated in this way is the planned date of birth for your baby.
This formula applies if your menstrual cycle regularly lasts 28 days. If the cycle time differs from this, you must either add or subtract this deviation at the end of the calculation - depending on whether your cycle is longer or shorter.

If you no longer know when your last period was, your doctor can calculate the delivery date by measuring your baby's crown-rump length.

Your gynecologist measures the crown-rump length and the head diameter during the regular ultrasound examinations.
Your doctor can then use tables to calculate the approximate date of delivery.
However, you should be aware that only a very small percentage of babies adhere to the calculated birth date at birth.
Pregnancy is very individual. So when exactly the baby is born cannot really be predicted exactly to the day.
Nevertheless, the calculation of the expected date of birth is important. After this appointment, for example, you can decide when you can go on maternity leave.

Find out what you need to know about the fertile days in the menstrual cycle in our next post.