What is the most accurate formula for calculating the due date?

Every pregnant mother wants to know when her baby will be born when she is pregnant. So here we need to popularize to pregnant mothers what the due date is? The so-called due date refers to the day when the fetus is fully grown and developed in the expectant mother's body and is about to be born. Since that day has not yet arrived, it can be understood as the "estimated time of delivery."

The due date can remind pregnant women of the safe time for the birth of their babies, but the due date is not the exact time of delivery. According to statistics from relevant medical scientists, only about 5% of pregnant women give birth on the due date. Pregnant women should be prepared for childbirth at any time when they reach the 37th week of pregnancy, but they don't need to be overly anxious and let nature take its course. If there are no signs of childbirth by the 41st week of pregnancy, pregnant women with certain conditions can be hospitalized for observation or appropriate induced abortion.

Because every pregnant mother cannot accurately determine the time of pregnancy, medicine requires that the expected date of delivery be calculated from the first day of pregnancy. The entire pregnancy period is 280 days (40 weeks) and 10 gestational months (each gestational month is 28 days).

The due date can remind pregnant mothers the safe time period for the birth of the fetus, so that pregnant mothers can make preparations for welcoming the baby in advance, and it is also a positive reference function for regular prenatal examination data. So how do you calculate the due date? Calculate based on the expected date of delivery: add 9 or subtract 3 from the month of the expected date of delivery to get the number of months of the delivery; add 7 to the day to get the expected date of delivery. For example: The due date of pregnancy is September 22nd. The calculation method of the due date is: month = 9-3 = 6 months, time = 22 7 = 29th, then the due date is June 29th.

Calculate based on the date of fetal movement: If the pregnant mother can't remember the due date, she can calculate it based on the date of fetal movement. Generally, fetal movement begins at 18-20 weeks of pregnancy. The calculation method is: for first-time pregnant mothers, it is the day the baby's fetal movement is added to 20 weeks; for pregnant mothers with two or three children, it is the day the baby's fetal movement is added to 22 weeks.

Calculate based on the ovulation temperature curve: take the last day of the ultra-low temperature section of the ovulation temperature curve as the ovulation period, and calculate backward from the ovulation period 264-268 days, or add 38 weeks.

Calculation based on B-ultrasound examination: When the doctor does B-ultrasound examination, he can measure the biparietal diameter of the fetal head, the brachiocephalic diameter and the femur length to estimate the gestational age and calculate the delivery date (this method is mostly used by doctors for B-ultrasound examination and diagnosis).

Calculate from the time when morning sickness starts: morning sickness usually occurs on the 6th week of pregnancy, which is 42 days after the expected date of delivery, and then calculate backward to 280 days to get the due date; so the calculation method is: due date = 34 weeks from the onset of early pregnancy reaction.

Estimate based on the height of the uterine fundus: If you can't remember the due date of your pregnancy, you can roughly estimate the date of delivery based on the height of the uterine fundus. At the end of the fourth month of pregnancy, the height of the uterus is between the navel and the upper edge of the toes (10 cm above the ischial tuberosity); at the end of the fifth month of pregnancy, the fundus of the uterus is 2 horizontal fingers below the navel (16-17 cm above the toes); at the end of the sixth month of pregnancy, the fundus of the uterus is level with the navel (19-20 cm above the toes); at the end of the seventh month of pregnancy, the fundus of the uterus is three horizontal fingers above the navel (22-23 cm above the toes); at the end of the eighth month of pregnancy, the fundus of the uterus is between the sternum and the navel (24-25 cm above the pubic area); at the end of the ninth month of pregnancy, the fundus of the uterus is 2 horizontal fingers below the sternum (28-30 cm above the toes); at the end of the tenth month of pregnancy, the height of the fundus of the uterus returns to the height of eight months, but the fetal abdominal circumference is larger than that of eight months.

Pregnancy calendar calculation method: Using the circular or disc-shaped pregnancy calendars currently sold on the market, you can compare the start date of the last menstrual period to calculate the gestational age and due date. This method may differ from the menstrual period reverse optimization method by 2-3 days.