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 estimated 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 (28 days per month), which is why there's the saying "ten months of pregnancy."Starting from the first day of your last menstrual period:
- For the due date month: If the month is greater than March, subtract 3. If it's less than March, add 9.
- For the due date day: If using the lunar calendar, add 14 days to the date of the last menstrual period. If using the Gregorian calendar, add 7 days.
The estimated due date is just an estimate.