The last menstrual period on April 17 is normal, and the theoretical due date is January 24 of the following year. The period of time from conception to delivery is called the gestation period, and the whole gestation period is 280 days. To estimate the expected date of labor by the last menstrual period, subtract three or add nine to the month of the last menstrual period, and add seven to the date, and the time obtained is the theoretical expected date of labor. However, due to the many factors affecting pregnancy and the different physical condition of each pregnant woman, the theoretical due date usually differs from the actual due date, within 1~2 weeks. In addition, pregnant women should also go to the hospital for checkups after pregnancy, and the doctor will make a comprehensive projection of the due date based on the ultrasound examination of the diameter of the gestational sac and the diameter of the fetal apex and buttocks. The influencing factors of pregnancy are complicated, if there is any discomfort promptly go to the hospital, under the guidance of the doctor for symptomatic treatment.