Patient's question:
How is the number of days of pregnancy calculated?Doctor's answer:
Hello, the normal gestation period is approximately 40 weeks. In medicine, the first day of the last menstrual period is often used as the start date for calculating the due date. The normal pregnancy duration is about 265 days, calculated from the day of fertilization. Ovulation occurs in the middle of the menstrual cycle, so a 40-week (280-day) pregnancy is two weeks longer than the actual time from fertilization. If a woman's menstrual cycle is 28 days long, a 280-day pregnancy is equivalent to ten months, as 28 days make up a month or a menstrual cycle, hence the saying "ten months of pregnancy."Starting from the first day of your last menstrual period:
- Due date month: If the month is greater than 3, subtract 3. If it's less than 3, add 9 to get the birth month.
- Due date day: If using the lunar calendar, add 14 days to the last menstrual period date for the birth date. If using the Gregorian calendar, add 7 days.
The due date is only an estimate.