How to calculate the due date of pregnant women most accurately

Pregnant mothers always look forward to meeting their babies during pregnancy, and expectant fathers also hope to know roughly when to take maternity leave. So how to calculate the due date of pregnant women most accurately? How to calculate the due date for normal and abnormal menstruation? The following editor will give you a detailed introduction.

How to calculate the due date

Morning sickness calculation method:

Usually women will experience their first morning sickness around 6 weeks of pregnancy, which is 42 days after their last menstrual period. At this point, add 250 days to get the expected date of delivery (the entire pregnancy is calculated as 40 weeks). However, each woman's morning sickness reaction is different, so this method is not absolutely accurate.

Fetal movement calculation method:

This calculation method is suitable for women who are not sure of the date of their last menstrual period. The first time a pregnant woman feels fetal movement is usually around 18-20 weeks of pregnancy, which is around the fifth month of pregnancy. If it is the first pregnancy, add 20 weeks to the first day of fetal movement, and add 22 weeks to the second pregnancy.

Menstrual calculation method:

Expectant mothers can calculate based on the date of the last menstrual period, using the method of month + 9/-3, date + 7. For example, if the last menstrual period is on January 8, then the expected month of delivery is 1+9=10, the date is 8+7=15, and the expected date of delivery is October 15. For another example, if the last menstrual period is on October 5, then the expected month of delivery is 10-3=7, the date is 5+7=12, which is July 12 of the following year. Of course, this calculation method assumes that the female menstrual cycle is stable at 28 days, but in reality, each female cycle is different, so the doctor will make appropriate adjustments.

B-ultrasound calculation method:

After a woman has an ultrasound, the doctor can make calculations based on relevant data, mainly the biparietal diameter of the fetal head, the crown-rump length and the femur length, to determine the approximate age of the fetus and calculate the expected date of delivery. This is also the method used by most doctors.

Basal body temperature calculation method:

If women have the habit of recording their basal body temperature, it will be more convenient. The ovulation day is often considered the fertilization day. As long as the last day of the low basal body temperature period is regarded as the ovulation day, and then 264-268 days are calculated, the expected date of delivery can be calculated. For friends with stable menstrual periods, this method is very accurate and can be tried.

Height of uterine fundus:

Generally speaking, this method is used in the middle and late stages of pregnancy. At the end of the eighth month of pregnancy, the fundus of the uterus will change. The fundus of the uterus is generally located in the middle of the xiphoid process and the umbilicus. At the end of the tenth month of pregnancy, it will return to the previous height, but the belly will appear larger.

How to calculate the due date most accurately

Normal calculation method

The calculation is based on the entire pregnancy period of 280 days. The specific method is: expected delivery month = month of the first day of the last menstrual period + 9 or -3, expected delivery days = days of the first day of the last menstrual period + 7. In this way, the calculated time is the expected delivery date. For example, if the last menstrual period is on February 1, then the month 2 plus 9 = November, and the day 1 plus 7 = the 8th, then the expected delivery date should be November 8. If the last menstrual period is after April, the method of subtracting 3 is used for calculation. If the last menstrual period is on April 2, then April - 3 = January of the following year, 2 plus 7 = 9 days, that is, January 9 of the following year is the expected delivery date. If calculated using the lunar calendar; the month calculation is the same, except that the date plus 7 days is changed to plus 15 days.

Abnormal calculation method

If a pregnant woman's previous menstrual cycles have exceeded her last menstrual period, the average number of days that exceeded should be added when calculating. For example, if sometimes it exceeds 5 days, sometimes exceeds 4 days, and sometimes exceeds 6 days, then 5 days should be added to the calculated number of days.

During the lactation period, if you are pregnant before menstruation resumes, or if you can't remember the date of your last menstruation, you can calculate it as follows: pregnancy vomiting starts around the 4th week after pregnancy and disappears at the 12th week (i.e. 3 months of pregnancy). When calculating, count 42 days from the date of vomiting onset as the date of your last menstruation, and then calculate it according to the general method. You can also calculate it according to the date of fetal movement. Generally, pregnant women feel irregular movements of the fetus' limbs in the uterus around the 20th week of pregnancy. When calculating, count 140 days from the date of fetal movement onset as the date of your last menstruation, and then calculate the expected date of delivery according to the general method.

If it is a leap year and the leap month falls during the gestation period, the month minus 3 should be calculated by minus 4.

If you cannot remember the date of your last menstrual period, morning sickness, or the start of fetal movement, you can also estimate the height of the uterine fundus:

At the end of the fourth month of pregnancy, the height of the uterine fundus is between the umbilicus and the pubic bone (10 cm above the pubic bone);

At the end of the fifth month of pregnancy, the uterine fundus is two horizontal fingers below the navel and 12 to 17 cm above the pubic bone.

At the end of the 6th month of pregnancy, the uterine fundus is level with the navel;

At the end of the 7th month of pregnancy, the uterine fundus is two horizontal fingers above the navel;

At the end of the 8th month of pregnancy, the fundus of the uterus is between the xiphoid process and the umbilicus;

At the end of the 9th month of pregnancy, the uterine fundus descends to two horizontal fingers below the xiphoid process;

At the end of 10 months of pregnancy, the height of the fundus of the uterus is the same as that at 8 months of pregnancy, between the umbilicus and the xiphoid process, but the abdominal circumference is larger than that at 8 months, and the part of the fetus that was born first has entered the pelvis.