The most reliable - it works 90%! - there is a due date calculated during the ultrasound examination between the 11th and 14th week of pregnancy. The doctor, seeing the fetus on the computer screen, measures the so-called CRL (distance from the top of the head to the baby's bottom) and enters the data into a computer program that calculates the age of pregnancy and the due date.
The due datewill be determined by the gynecologist of course. Usually, he does it on the first visit, after taking a medical history. However, you can also play predicting the future yourself and do it yourself.
Calculating the due date with a calendar in hand
»Based on the date of conception.
Pregnancylasts 267 days, 38 weeks, or 9 and a half lunar months from conception. If you can indicate its exact date, you can easily calculate the expected time of delivery (predicted, i.e. assuming that there will be no complications and the pregnancy will be of an ideal, book-like length).
However, many women do not know the exact moment of getting pregnant (doctors say that this applies to more than 2/3 of patients), besides, the egg is capable of fertilization for almost a week, therefore such calculations may be inaccurate.
» Based on the first day of your last periodof your period .
Recall the date your last period started. You will calculate the due date by adding 7 days to it, and then to the result - 9 months (this is the so-called Naegele rule).
Here is an example: The first day of your last period is May 10, 2010. Add 7 days - you have May 17. Add 9 months and you will get February 17, 2011. The average gestation time calculated by this method is 281 days, 40 weeks or 10 lunar months. The above rule and calculations are valid only for women who had regular cycles of 28 days before pregnancy.
This is just an approximate date
Only 4 percent pregnant women give birth exactly to the day at the specified date. Women who had long monthly cycles generally give birth after the appointed term, while women who had cycles shorter than 28 days give slightly earlier. So don't panic when "zero hour strikes" and labor doesn't start. Having a baby up to 2 weeks after the calculated date is safe for the mother and the baby. The most important thing is pregnancylasted at least 37 weeks. Such a pregnancy is treated as a physiological, term pregnancy.
For longer or shorter periods, this rule does not work. It should be modified accordingly - ask the gynecologist in charge of your pregnancy about it.
» Based on ready-made formulas, calculators and tables.
If you don't want to play arithmetic, use our CALCULATE BIRTH DATE calculator, which will calculate the date solutions.
» Based on the feeling of the first fetal movements.
Previously, before the ultrasound era, it was one of the methods of predicting the date of birth of a child. The first baby movements are usually felt at the end of the 20th week of pregnancy, and multiparous women at the end of the 18th week of pregnancy. So from that moment it is enough to add 20 weeks (when you give birth for the first time) or 22 weeks (when you are expecting your next baby).
However, calculating the due date on this basis turns out to be very inaccurate. It is not uncommon for multiparous women to feel the first movements of the fetus at the end of the 16th week of pregnancy, and the elements are often unable to provide the date of the first movements. Therefore, this method is rather to confirm the calculated date.