Usually, pregnant women start to gain weight significantly around the 4th month of pregnancy, but there are individual differences. After the fourth month of pregnancy, the early pregnancy reaction basically disappears, and the pregnant woman’s appetite returns or even increases greatly. At the same time, the fetus in the uterus begins to develop rapidly and the fetus’ weight increases, resulting in the need for the pregnant woman to consume more nutrients and energy to supply the fetus’ development, thus causing the pregnant woman to gain weight gradually. Weight gain during pregnancy is usually caused by the combined effect of estrogen and progesterone, which affects the distribution of fat in the body and leads to weight gain. Pregnancy weight gain mainly comes from the uterus and its contents, breasts, increased blood volume, interstitial fluid, and small amounts of maternal fat and protein stores, with an average maternal weight gain of 12.5 kg during pregnancy. maternal weight gain can affect the near and long-term health of the mother and child. Excessive maternal weight gain can increase the risk of macrosomia, obstructed labor, birth injury, and gestational diabetes; insufficient maternal weight gain is associated with fetal growth restriction, prematurity, and low birth weight, so weight management should be emphasized. Pre-pregnancy BMI can be determined during the first maternity check-up of pregnant women, and personalized guidance on weight gain, diet and exercise for pregnant women can be provided. It is recommended to have a reasonable diet, balanced nutrition, small and frequent meals, strictly prohibit overeating, avoid intake of high-fat and high-sugar foods, match aerobic exercise and pay attention to ensure sufficient rest during pregnancy.