Regarding the expected date of delivery, why are some people ahead of schedule and others behind? How to calculate the expected date of delivery?

The reason why some babies are born before the expected date of delivery and some babies are born after the expected date of delivery is actually related to our irregular menstruation. If a woman's menstruation is not particularly regular before pregnancy, then the time of her last menstruation is definitely not so accurate. As we all know, the expected date of delivery is calculated based on the last menstruation, so naturally it will not be so accurate.

In fact, many people don't know how to calculate the expected date of delivery. We usually say that pregnancy is 10 months, and a month is about 30 days, so people may think it is 300 days. But it's not like this. The pregnancy cycle is calculated according to 28 days per month, which means that 10 months is 280 days. The general method for doctors to calculate your expected date of delivery is to add nine or subtract three from the month of your last menstruation, and then add about one week to this date, which is the expected date of delivery of pregnant women.

However, we will find that the dates predicted by doctors are mostly inaccurate, and only about 1% of children can be born on the dates predicted by doctors. Some people may say, why is this? Is it because the doctor miscalculated? Actually, it's not like this. How can a doctor make a mistake? After all, people are professionals. So the biggest reason is that some women's menstruation is not so accurate, and they may remember that the date is not so accurate.

What's more, the expected date of delivery is just a date predicted by everyone, which does not mean that you will be born there. If a doctor can calculate this thing so accurately, he may not be a doctor, but a fortune teller. In fact, the average baby is full-term in the stomach until 37 weeks, and the best delivery period is about 39 weeks to 40 weeks.