The last menstrual period was on April 20, and in usual circumstances, the expected date of delivery is January 27 of the following year. Since it is difficult to accurately estimate the time of conception for every pregnant woman in the clinic, in medical practice, it is usually calculated from the first day of the last menstrual period, and the whole pregnancy lasts for a total of 280 days. However, due to the fact that the circumstances of labor and physical fitness of each woman vary greatly, the theoretically estimated due date may be different from the actual date of delivery. To calculate the due date according to the last menstrual period, the month needs to be subtracted from three or added to nine, and the date needs to be added to seven, and the resulting time is the theoretical due date. Due to the many factors affecting the pregnancy, it is recommended that pregnant women go to the hospital to improve the physical examination and ultrasound and other tests, so that the doctor of obstetrics can confirm the expected date of delivery, and do the labor examination in time, so as to avoid being affected by the undesirable factors. If there is any discomfort during pregnancy, you should go to the hospital in time and get symptomatic treatment under the doctor’s guidance.