I got pregnant in September, but in which month did I give birth to the baby?

Patient's question:

No

Doctor's answer:

The method for calculating the estimated due date is: add 9 months (or subtract 3 months) to the last menstrual period's month, and add 7 days to the last menstrual period's day. If the menstrual cycle was irregular before pregnancy or the cycle was long, it is recommended to use the ultrasound examination result as the reference.