How Many Weeks in a Month of Pregnancy?

One month of pregnancy equals four weeks. In medical terms, a month is defined as 28 days, which is exactly four weeks. A natural month ranges from 28 to 31 days, leading to the existence of the sayings of nine-month pregnancy and ten-month pregnancy. Since it is difficult for every pregnant woman to accurately determine the time of conception, medically, the expected date of delivery is calculated from the first day of the last menstrual period. The entire pregnancy period lasts for 280 days, or 10 pregnancy months (each pregnancy month being 28 days). Delivery within 38-42 weeks of pregnancy is considered full-term. Due to variations in menstrual cycle lengths among women, a 1-2 week discrepancy between the estimated and actual due dates is considered normal. The expected month of delivery is calculated by adding 9 or subtracting 3 to the month of the last menstrual period, and the expected day of delivery is calculated by adding 7 to the day. For example, if Ms. Liu's last menstrual period was on March 13, 2008, her estimated due date would be around December 20, 2008. If Ms. Li's last menstrual period was on May 28, 2008, her estimated due date would be around March 5, 2009. Alternatively, the expected date of delivery can be calculated by counting backward from the first day of the last menstrual period to the 280th day. The last day of the low-temperature phase on the basal body temperature curve can be used as the ovulation day, and the expected date of delivery can be estimated by counting backward from the ovulation day for 264-268 days, or adding 38 weeks. Morning sickness typically occurs around the end of the sixth week of pregnancy, which is 42 days after the last menstrual period. Counting backward from this point to 280 days yields the estimated due date.