The expected date of labor is only a prediction of the delivery date, which is only an approximate range of the time of birth and will not be very accurate. It is difficult for every pregnant mother to accurately determine the time of conception, therefore, it is medically prescribed to calculate the due date from the first day of the last menstrual period. Commonly used methods of calculating the due date include calculating it from the day of fertilization, ultrasound test method, and calculating the due date by using a formula. The due date is usually 280 days, 10 gestational months, and 40 weeks of pregnancy. The due date can be affected if a woman has irregular menstrual periods, irregular ovulation, and so on. Therefore, the actual due date should be judged according to the woman’s physical condition and examination results. It is calculated from the 1st day of the woman’s last menstrual period, and if the menstrual cycle is advanced or staggered, the due date will be advanced or staggered as well. If the expected date of delivery is more than 2 weeks without effective contractions, it is called an overdue pregnancy, and it is necessary to go to the hospital in time for checkups, such as ultrasound, to find out whether the placenta is aging or not, whether the amniotic fluid is too small, etc., and combine with the doctor’s opinion to comprehensively assess the mother, and if necessary, assist in intervening and delivering the baby as soon as possible to prevent the decline of the function of the placenta.