Weight management during pregnancy starts from the preparation period and continues throughout pregnancy until after delivery. 1.Preparation period: When you are ready to get pregnant, calculate your body mass index BMI (BMI = weight Kg/height m2). It is best to control your weight to a normal BMI before you get pregnant. BMI <18.5 is low weight, it is recommended to strengthen nutrition. BMI 18.5-24.9 is normal weight, you can prepare for pregnancy. BMI 25.0-29.9 overweight, exercise and diet adjustment. BMI>=30 obese, exercise plus diet adjustment, reduce weight and then get pregnant. 2.Early pregnancy: before 13 weeks of pregnancy, because the embryo is very small, it does not need much nutrition, so you can maintain a normal diet and do not need too much nutrition. Weight gain should be controlled within 2Kg. 3.Middle and late pregnancy: after 13 weeks of pregnancy, according to the pre-pregnancy body mass index BMI, control the weight growth. BMI<18.5 low weight, 0.51Kg per week, 12.5-18Kg during pregnancy; BMI18.5-24.9 normal weight, 0.42Kg per week, 11.5-16Kg during pregnancy; BMI25.0-29.9 overweight, 0.28Kg per week, 7.5-11.5Kg during pregnancy; BMI>=30 obese, gaining 0.22Kg per week and 5.0-9.0Kg throughout pregnancy. 4, normal physiological weight gain during pregnancy includes: fetus 3.2-3.6Kg, amniotic fluid 0.9Kg, placenta 0.7Kg. about 5Kg, which will be reduced after delivery. Hoarding of fat 2.7-3.6Kg, breast enlargement 0.45-1.4Kg in preparation for breastfeeding. Blood volume increases by 1.4-1.8Kg, extravascular fluid increases by 0.9-1.4Kg, and the uterus increases by 0.9Kg. It is excreted in the form of sweating and urination during the puerperium. 5.Postpartum weight retention: Generally, the weight gain is 3-4Kg compared with pre-pregnancy. weight retention exceeds 5Kg, and the risk of gestational diabetes, gestational hypertensive disease, preterm delivery and cesarean section increases in the next pregnancy.