How to know the exact number of days of pregnancy

After a woman becomes pregnant, she will usually go to the hospital to confirm the pregnancy, and the doctor will give her the number of days of pregnancy, but it is not very accurate. So how can we know the exact number of days of pregnancy? The hospital will use some tests to determine how far along the pregnancy is, such as urine and blood tests. More calculation methods are to calculate the number of days of pregnancy based on the time of the woman's last menstrual period, or the woman herself knows the day she conceived.

How to determine the number of days of pregnancy

The onset of pregnancy can be determined in several ways. One is to detect hormones produced by the newly formed placenta. Clinical urine and blood tests can detect pregnancy within 6-8 days after conception. Home urine tests usually take 12-15 days to be effective. Both methods can only detect pregnancy but not the date of conception. Pregnancy can also be confirmed by the interruption of menstruation. Interruption of menstruation precedes any early pregnancy symptoms (such as morning sickness). In fact, doctors usually calculate the day of conception (i.e. the age of the embryo) based on the first day of a woman's last menstrual period. Unless sexual intercourse is rare, the exact date of conception is unknown.

Since the date of conception is difficult to determine, the embryo and fetus are only distinguished scientifically and not in actual pregnancy. Conception can be further divided into fertilization when the egg meets the sperm in the fallopian tube and subsequent implantation.

How to calculate the due date

1. Calculated based on the last menstrual period

This method is the most commonly used and simplest. If the pregnant woman has a regular menstrual cycle, with menstruation every 28-30 days, and the last menstrual period is remembered accurately. You can use the formula to calculate: starting from the first day of the last menstrual period, subtract 3 or add 9 to the month, and add 7 to the day. If calculated according to the lunar calendar, the month should be added by 9 or subtracted by 3, and the date should be added by 14.

For example, if the first day of the last menstrual period is April 24, 2002, the expected date of delivery should be January 31, 2003; if the first day of the last menstrual period is April 24, 2002 in the lunar calendar, the expected date of delivery should be February 8, 2003 in the lunar calendar.

For women who have menstruation every 3 weeks, the pregnancy period should be 280 days - 1 week = 39 weeks.

For women who have their periods every 4 weeks, the pregnancy period should be 280 days = 40 weeks.

For a woman who has her period every 5 weeks, her pregnancy period should be 280 days + 1 week = 41 weeks.

2. According to the date of sexual intercourse that caused pregnancy

The 266th day from the date of sexual intercourse is the expected date of delivery.

3. Calculate according to the date of early pregnancy reaction

Some women have irregular menstrual cycles, or have forgotten the date of their last menstrual period, or have become pregnant again after giving birth or having an abortion but have not had their period yet. As long as they remember the time when early pregnancy symptoms such as nausea and vomiting occurred, they can use this to calculate the expected date of delivery. Since early pregnancy reactions usually occur around 6 weeks of pregnancy, the calculation formula is:

Due date = date of onset of early pregnancy symptoms + 34 weeks.

4. Calculated by the height of the uterine fundus

By comparing the measured uterine fundus height with the normal value table, the equivalent gestational age can be found. Add 40 weeks to this date to get the expected date of delivery.

Generally speaking, the actual delivery date can differ from the estimated due date by 1 to 2 weeks.

5. Calculate by the date of fetal movement

The fetal movement of primiparas occurs around the 18th week of pregnancy. Multiparas, because of their experience, can feel the fetal movement 2 weeks earlier than primiparas, that is, at the 16th week of pregnancy. Therefore, the calculation formula is:

The expected date of delivery for a primipara = the date when fetal movement occurs + 22 weeks.

The expected date of delivery for a multiparous woman = the date of fetal movement + 24 weeks.

Through the above methods, pregnant women can calculate the date of their baby's birth by themselves. In addition, if the pregnant woman can not remember the time of her last menstrual period, has no early pregnancy reaction, and has not felt fetal movement, the doctor can use B-ultrasound and the height of the uterine fundus to help estimate the expected date of delivery.

6. Calculate according to B-ultrasound results

By measuring the gestational sac, fetal sitting height, biparietal diameter of the fetal head or fetal femoral length under B-ultrasound and comparing the measured values ​​with the normal value table, the equivalent gestational age can be found. Add 40 weeks to this date and the result is the expected date of delivery.