If a woman’s menstrual cycle is usually regular, she can project the expected date of labor through the last menstrual period, i.e., the number of months of the pregnant woman’s last menstrual period minus 3 or plus 9, and the date of the last menstrual period plus 7, which is the expected date of labor. However, if the menstrual cycle is not regular, the expected date of labor can be estimated by the size of the gestational sac and the biparietal diameter of the fetus. 1. Regular menstrual cycle: If you have a regular menstrual cycle, the expected date of labor is 40 weeks, counting from the first day of your last menstrual period to 280 days. 2. Irregular menstrual cycle: If the menstrual cycle is not regular, ovulation will not be particularly regular, the expected date of delivery can not be calculated by the date, you need to do ultrasound to check the size of the gestational sac, the size of the embryo buds, the fetal biparietal diameter and so on, to estimate the expected date of delivery. The due date is an approximate date, and delivery within two weeks before or after the due date is considered a full-term pregnancy, so it is recommended that you follow your doctor’s advice.