For women who normally have regular periods, the expected date of delivery is calculated as the month of the last menstrual period minus 3 or plus 9 and the date plus 7. The expected date of labor can be deduced from the time of the last menstrual period, and is only applicable to women who have regular menstrual periods. It is calculated as the month of the last menstrual period minus 3 or plus 9, which is the month of the expected date of labor, and the date is the first day of the last menstrual period plus 7. There will be some discrepancies in the estimation of the expected date of labor for women with irregular menstruation using this method. The due date is not completely accurate, and the calculated due date may differ from the actual date of delivery. It is very important to calculate the due date so that your doctor can make a preliminary judgment on whether the development of the fetus is in line with the week of pregnancy and intervene medically if necessary. Pregnant women who want to predict their due date are advised to consult a medical professional to avoid blindly calculating the due date on their own.