What is the due date calculator and what is the due date based on?

How do you know the due date of ovulation?

As for the question of how to calculate the due date of ovulation, in fact, if we regard the day of ovulation as the day of fertilization, then from the day of ovulation, about 38 weeks, that is, about 266 days is the due date of the expectant mother. Of course, the due date is only an approximate estimate, and it does not mean that the expectant mother will enter labor on the due date.

In addition to calculating the due date on the day of ovulation, what are the methods for calculating the due date?

1) Estimated based on the time of the last menstrual period.

Generally speaking, the doctor will subtract 3 (9 if it is insufficient) according to the month of the mother-to-be's last menstrual period, or add 8 to the direct month, add 7 to the number of days, and the final calculated date is the time of the due date. For example, if the last menstrual period occurs on April 5, the expected date of delivery should be calculated to be around January 12 of the following year.

2) Extrapolation based on uterine size.

In order to calculate the due date, there is not only one method, in which the doctor can also determine the number of weeks of pregnancy according to the height of the uterine fundus of the expectant mother. The main method is to use ultrasound to measure the size of the fetal sac, the length of the fetal head to the hips, and the interparietal diameter on both sides of the fetal head, etc., and finally the number of weeks of pregnancy can be well calculated.

In fact, the method of calculating the due date by ovulation day is a very common method in daily life, but the calculation of the due date is not completely accurate and can only be used as a reference.

Since it is difficult for every pregnant woman to accurately determine the time of conception, it is medically prescribed that the due date is calculated from the first day of the last menstrual period, and the entire pregnancy period is 280 days, 10 gestational months (each gestation month is 28 days, that is, 40 weeks).

From the beginning of the month of the last menstrual period, add nine months and seven days to the expected date of delivery.

The time of the last menstrual period can be calculated according to the doctor's diagnosis.

The expected date of delivery is calculated as follows:

1. Calculated according to the last menstrual period: the month of the last menstrual date is added by 9 or minus 3 to be the number of months of the expected date of delivery; The number of days plus 7 is the expected date of delivery. For example:

Ms. Zhang's last menstrual period was March 13, 2008, and her expected date of delivery was December 20, 2008. Ms. Li's last menstrual period was May 28, 2008, and her expected date of delivery was about:

March 5, 2009 can also be extrapolated from the first day of the last menstrual period to the 280th day, which is the expected date of delivery.

2. Calculate according to the date of fetal movement: If you can't remember the date of your last menstrual period, you can calculate it according to the date of fetal movement. Usually fetal movements begin at 18-20 weeks after pregnancy. The calculation method is as follows: the day of fetal movement plus 20 weeks for primiparous mothers; In multiparous women, the day of fetal movement plus 22 weeks is added.

3. Calculate according to the basal body temperature curve: take the last day of the low temperature section of the basal body temperature curve as the ovulation day, and calculate 264-268 days backwards from the ovulation day, or add 38 weeks.

4. Estimation according to B-ultrasound examination: The doctor can estimate the gestational age and calculate the expected date of delivery by measuring the diameter between the fetal head and biparietal head, head and hip length and femur length when doing B ultrasound.

5. Estimation from the time of morning sickness: morning sickness generally occurs at the end of 6 weeks of pregnancy, that is, 42 days after the last menstrual period, and the expected date of delivery is calculated backwards to 280 days.

From the first day of the last menstrual period, the month is minus 3 or 9, and the number of days is added 7.

The entire pregnancy period is about 40 weeks, which is about 9 months and 7 days, and the expected date of delivery can be estimated by the time of the last menstrual period. The calculation method is calculated based on the first day of the last menstrual period, subtracting 3 or adding 9 to the month, and adding 7 to the number of days. However, the actual date of delivery may differ from the estimated expected date of delivery by 1 to 2 weeks, and if the date of the last menstrual period of the pregnant woman is not clear or the menstrual period is inaccurate, the doctor needs to calculate the due date on behalf of the pregnant woman.

Factors influencing the accuracy of the due date.

1. Menstrual cycle. According to the average, a woman's menstrual cycle before pregnancy is a cycle of 28 days. But not every pregnant woman's cycle is 28 days. As a result, the expected date of delivery is less accurate when calculated based on the time of the last menstrual cycle.

2. Individual differences.

Since each pregnant woman has a different ovulation cycle before conception, the ovulation date may be earlier or later. Moreover, there are individual differences in the physique of pregnant women, for example, some pregnant women do not have very obvious symptoms of morning sickness during pregnancy, so it is not accurate to calculate the expected date of delivery based on morning sickness. This will result in a discrepancy between the actual production date and the expected date of delivery.

3. The date is not accurate.

When the first prenatal physician asks about the last menstrual period, the actual date is not clear or confused, which affects the accuracy of the estimated due date.

4. Other factors. In general, ultrasound is one of the most accurate ways to estimate the expected date of delivery.

1. Now that there is a ** due date calculator function on the Internet, many pregnant women are worried about the accuracy of the expected date calculator. Let's take a look at whether the due date calculator is accurate.

Empirical Steps:

3. The first aspect: **The expected delivery date calculator is still relatively accurate, and the operation is relatively simple. However, when entering information, it must be accurate, and you can't make mistakes, otherwise there will be a big deviation.

4. The second aspect: **The expected date calculator can only calculate an approximate range, because this is still very difficult**, and everyone's fluctuation is relatively large. So this time can only be used for reference.

5. The third aspect: the whole pregnancy period is about 40 weeks, that is, about 9 months and 7 days, and the expected date of delivery can be estimated by the time of the last menstruation. The calculation method is calculated based on the first day of the last menstrual period, subtracting 3 or adding 9 to the month, and adding 7 to the number of days. That's how it works.

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