Important formula for the special day
One thing is clear: your unborn child has no sense of higher maths yet. It is therefore very unlikely that it will keep exactly to its pre-calculated due date. Nevertheless, it is important to determine the expected date of birth.
As a pregnant woman, you naturally want to know as soon as possible: When will my child be born in purely mathematical terms? However, the calculated date of delivery also provides information about which week of pregnancy the expectant mother is currently in. This in turn determines the timing of certain check-ups during pregnancy (e.g. the test for gestational diabetes between the 25th and 28th week or the examination intervals shortened to two weeks from the 32nd week). In this way, the determined date of birth determines the type and frequency of check-ups during pregnancy as well as the professional assessment of whether the foetus is developing in line with its age. At the same time, the start of your maternity protection period at work is determined according to your child's expected birthday. You can see how important it is to calculate this date.
You may be holding your Maternity passport already in your hands. The "officially" calculated date of birth is entered on page six.
But it could also be that you have just taken a pregnancy test from the pharmacy and two "magic" two lines are now showing you: You are pregnant! You will now have the fact that you are expecting a child confirmed by a registered midwife or at your gynaecologist's practice as soon as possible. However, if you want to know immediately when your baby is expected to be born, you can calculate the "unofficial" due date yourself.
There are numerous calculators on the Internet that you can use. Or you can simply do the maths yourself. Either way, you will need the following date: either the Day of fertilisation (conception) or the first day of your last period. With this information, it is easy to find out the expected date of delivery using the classic Naegele method. The formula for this was invented by the German gynaecologist Franz Naegele (1778 - 1851).
The formula is based on a 28-day cycle and works as follows:
Here's an example: Let's take 21 April 2021 as the first day of your last period. Now subtract three months from this date, which gives you 21.1.2021. Now add seven days and you arrive at 28.1.2021. You add another year to this date - and end up with the expected delivery date: 28.1.2022.
Some women also have a longer or shorter cycle than 28 days. No problem: first determine the expected date of birth using one of the above formulas based on the 28-day cycle. Then simply add your additional cycle days to the result or subtract the missing days from the result. In my example, 28 January 2022 was calculated as the expected delivery date for the 28-day cycle. With a 30-day cycle, the due date would then be 30/01/2022 (28/01/2022 + 2 days), with a 25-day cycle, your child would be born on 25/01/2022 (28/01/2022 - 3 days). You can also calculate your baby's due date here: https://notdiensthebamme.de/geburtsterminrechner/
Ultimately, however, any determined date of birth only indicates the approximate time for the birth of a mature child. Because, as I said, babies can't do maths yet. In fact, only around five per cent of children are born on the exact date calculated. Most of the others are born up to two weeks earlier or later.
The calculated due date is, to be precise, the middle of the birth period in which your baby is likely to be born. In the first three months of pregnancy, it can also happen that your gynaecologist corrects the originally calculated delivery date. This would be the result of the first ultrasound scan (link to text ultrasound scans) between the 9th and 12th week of pregnancy. Sometimes these images show a different size of the child than it should be according to the calculated due date. During this ultrasound, the so-called crown-rump length (SSL) of your child is measured with millimetre precision. This refers to the length from the highest point of the head (crown) to the base of the bum (rump). As unborn children develop almost identically in the first 12 weeks of pregnancy, the size of a foetus during this period provides fairly reliable information about its actual age. If necessary, the calculated delivery date is adjusted accordingly
