The duration of fetal growth in the mother’s body: 40 weeks or 280 days. Method of calculating the expected date of delivery: The month of the last menstrual period minus 3 (plus 9 if not enough) is the month of the expected date of delivery; the day of the start of the last menstrual period plus 7 is the expected date of delivery. The time when pregnancy reaction appears: around the 4th week of pregnancy. Time of disappearance of pregnancy reaction: around 12 weeks of pregnancy. Time of first prenatal checkup: after menopause. Time of self-recognition of fetal movement: 16-20 weeks of gestation. Normal number of fetal movements: about 30-40 times per 12 hours, should not be less than 15 times. The number of fetal movements measured in the morning, midday and evening should be multiplied by 4. Time of occurrence of preterm labor: within 28-37 weeks of gestation. Normal number of fetal heart sounds: 120 to 160 beats per minute. Premature pregnancy: the usual regular menstruation, 14 days after the expected date of delivery. Signs of preterm labor: redness, vaginal fluid, abdominal distension and pain, 1 uterine contraction every 5 to 6 minutes, each lasting more than 30 seconds. The above numbers should be grasped by pregnant women, and when there are special circumstances, they should go to the hospital for examination in time.