The due date is only a prediction of the delivery date and is only an approximate range of the time of delivery and will not be very accurate. It is difficult for every pregnant mother to accurately determine the time of conception. Therefore, medical regulations stipulate that the due date is calculated from the first day of the last menstrual period. Common methods of calculating the due date include calculating it by the day of fertilization, the ultrasound test method, and using a formula to calculate the due date. The due date is usually 280 days, 10 gestational months and 40 gestational weeks. If a woman has irregular menstruation, irregular ovulation, etc., the due date will be affected. Therefore, the actual due date should be judged according to the woman’s physical condition and examination results. The due date is calculated from the first day of the woman’s last menstruation, and if the menstrual cycle is early or wrong, the due date will also be early or wrong. If the expected date of delivery is more than 2 weeks and there is no effective contraction, it is called overdue pregnancy, so it is necessary to go to the hospital in time for examination, such as ultrasound examination, to know whether the placenta is aging or not, whether the amniotic fluid is too small, etc., and to make a comprehensive assessment of the woman with the doctor’s opinion, and if necessary, to assist intervention to deliver as soon as possible to prevent the placenta from declining.