For women with regular periods, the due date can be estimated based on the first day of the last menstrual period. For women who have irregular periods and do not remember when their last period was, the expected date of labor is based on the first ultrasound of the early pregnancy. Therefore, for irregular menstruation and not remembering the last menstruation, the ultrasound result is used to estimate the expected date of labor, and if the menstruation is regular, the expected date of labor should be estimated according to the first day of the last menstruation. Generally speaking, the expected date of labor is calculated by subtracting the month of the last menstrual period from 3 or adding 9 days and 7 days to the expected date of labor. But nowadays there are many women who may not give birth on their due date. The due date refers to 40 weeks of pregnancy, and nowadays, medically speaking, it is not considered premature labor after 37 weeks, so don’t be obsessed with whether you must have your baby on your due date or not.