1, according to the time of the last menstrual period: calculated from the first day of the last menstrual period, the entire pregnancy 280 days, 10 gestational months (28 days per gestational month), menstrual cycle for 28 days, the expected date of delivery = the first day of the last menstrual period + 280 days, such as menstrual cycle of 30 days, can be calculated in the last after the date of +2; or according to the rules of the Nigel, the month ≥ 4, the expected date of delivery = month-3, date +7; month ≤ 3, the expected date = month +9, date +7. This method is more accurate. According to Nigel’s rule, when the month is ≥4, the expected date of delivery is month-3 and date+7; when the month is ≤3, the expected date of delivery is month+9 and date+7. This method is more accurate and is commonly used by obstetricians and gynecologists at present; 2. According to the time of early pregnancy reaction: Early pregnancy reaction generally refers to the fact that in the 6 weeks after menopause, the level of human chorionic gonadotropin in the body of the pregnant woman is increased, which causes a series of nausea, fatigue, dizziness, vomiting and other reactions in the morning. Expected date of delivery = date of onset of early pregnancy reaction + 34 weeks. It should be noted that the period of the beginning of vomiting can vary from person to person, and cannot be used as an accurate calculation method; 3, according to the date of fetal movement: the date of fetal movement is different between primigravid women and transgravid women, with the former occurring more often in the 18th week of pregnancy, and the latter occurring more often in the 16th week of pregnancy. The expected date of delivery for primigravida = the date of fetal movement + 22 weeks; the expected date of delivery for primigravida = the date of fetal movement + 24 weeks; 4, according to the ultrasound projection: this method is a more accurate method, the doctor according to the ultrasound detection of the fetal head biparietal inter-parietal diameter, the length of the head and buttocks and the length of the femur, the age of the fetus can be estimated, and can be projected to the expected date of delivery.