How Many Days Are in a Pregnancy Term?

Update Date: 2024-07-11 Source: Network

Pregnancy Duration and Calculation of Expected Date of Delivery

The pregnancy duration is 280 days, which is equivalent to 10 gestational months. Pregnancy duration refers to the time period from conception to childbirth. Pregnancy indicates the presence of an embryo or fetus in a woman's body, which can be one or multiple. The expected date of delivery (EDD) is typically calculated based on the last menstrual period (LMP). This is done by adding 9 months to the LMP month or subtracting 3 months, and adding 7 days to the LMP date, resulting in the EDD. According to medical regulations, the EDD is calculated from the first day of the LMP, with the entire pregnancy lasting 280 days or 10 gestational months. Delivery within 38 to 42 weeks of gestation is considered full-term. Due to variations in menstrual cycles among women, there can be a 1 to 2-week discrepancy between the estimated EDD and the actual EDD, which is considered normal.

Calculation of the Expected Date of Delivery:

1. Based on the Last Menstrual Period: Add 9 months to the LMP month or subtract 3 months, and add 7 days to the LMP date to determine the EDD. For example, if the LMP is March 13, 2008, the EDD would be approximately December 20, 2008. Alternatively, counting backward from the first day of the LMP to the 280th day also gives the EDD.

2. Based on the Date of Fetal Movement: If the LMP date is not known, the date of fetal movement can be used to estimate the EDD. Fetal movement typically begins between the 18th and 20th weeks of pregnancy. The calculation is: for first-time mothers, add 20 weeks to the date of fetal movement; for multiparous mothers, add 22 weeks.

3. Based on the Basal Body Temperature Curve: The last day of the low-temperature phase of the basal body temperature curve is considered the ovulation day. From the ovulation day, count backward 264 to 268 days, or add 38 weeks, to determine the EDD.

4. Based on Ultrasound Examination: During an ultrasound examination, the biparietal diameter, head-to-rump length, and femur length of the fetus can be measured to estimate the gestational age and calculate the EDD (this method is primarily used by doctors for diagnostic purposes).