Is the estimated due date accurate?

We all know that pregnant women need many more prenatal checkups during pregnancy. When they just start to get pregnant, the prenatal checkups they do are generally B-ultrasound, which is cheap and convenient. Some people choose to use B-ultrasound to calculate the expected date of delivery, because the expected date of delivery is calculated based on the growth of the baby in the body and is also related to the mother's menstrual cycle. So is B-ultrasound accurate in calculating the expected date of delivery?

How to calculate the due date?

In order to be able to prepare early, many expectant parents want to know when their baby will be born, so many people will calculate the expected date of delivery of pregnant women. So, what are the methods for calculating the due date? In fact, there are several methods for calculating the due date.

The first is the last menstrual period method, which adds 9 or subtracts 3 from the month of the last menstrual period and adds 7 to the day to get the month and date of the expected delivery date. If you can no longer remember the time of your last menstrual period, you can estimate it based on the time of fetal movement. Generally speaking, the first fetal movement occurs around 18 to 22 weeks of pregnancy, and the fetal movement of a pregnant woman who is pregnant again will generally occur two weeks earlier than that of a primipara. Therefore, the method for calculating the due date is: the due date of a primipara = the date of fetal movement + 20 weeks. The expected date of delivery for a multiparous woman = the date of fetal movement + 22 weeks.

Alternatively, it can be estimated based on basal body temperature. The lowest segment of the basal body temperature curve is the female's ovulation time, so the last day of the low temperature segment of the basal body temperature curve can be taken as the ovulation day, and then the expected delivery date of the pregnant woman can be obtained by calculating back 264-268 days from the ovulation day, or adding 38 weeks. In addition, it can also be estimated based on B-ultrasound examination. When doctors perform B-ultrasound, they can estimate the gestational age and work out the expected date of delivery of the pregnant woman after measuring the biparietal diameter of the fetal head, the crown-rump length and the femur length. This method is mostly used by doctors for B-ultrasound diagnosis. There is also a method that only professionals know, which is to roughly estimate the expected date of delivery of a pregnant woman based on the height of the fundus of the uterus.

Is B-ultrasound accurate in predicting the date of delivery?

Nowadays, many methods can help expectant parents calculate the due date. If you go to the hospital for a prenatal check-up, the doctor will generally calculate the due date of the pregnant woman through B-ultrasound. So, many people want to know, is B-ultrasound accurate in calculating the expected date of delivery?

Doctors will use ultrasound to check the embryo length, crown-rump diameter and other items in the early pregnancy period (before 14 weeks of pregnancy) to estimate the last menstrual period, thereby determining the gestational age and correcting the expected date of delivery. Generally speaking, doctors use this method to calculate the expected date of delivery for pregnant women, and this calculation is more accurate, with the error generally not exceeding 5 days. However, it should be noted that if the fetal age is determined based on B-ultrasound in the second or third trimester, the error may be relatively large, even as large as 2 weeks. Therefore, if you want to determine the expected date of delivery of a pregnant woman through B-ultrasound, it is best to do it in the early stages of pregnancy.

In addition, the expected date of delivery of a pregnant woman can also be calculated based on the last menstrual period. If the due date calculated based on the actual last menstrual period and the due date calculated by B-ultrasound are no more than one week apart, they are generally more accurate and there is no need to recalculate the due date. In fact, the due date is just an approximate time, not the exact date of birth of the baby. It is only used as a reference. Not many pregnant women give birth on the due date. Most of them give birth before or after the due date.