Four months pregnant, that is, 16 weeks before the weight gain of about 3 pounds normal, normal weight growth range and pre-pregnancy body mass index (weight and height of the square of the ratio), early pregnancy due to nausea, vomiting pregnancy reaction, pregnant women weight gain is not obvious or even reduce the middle and late pregnancy, that is, after 13 weeks of weight gradually increase. Weekly weight gain during pregnancy is related to the pre-pregnancy body mass index, if pre-pregnancy belongs to the low weight, weekly can increase 0.51kg or so, if pre-pregnancy belongs to the normal weight, weekly weight gain can be 0.42kg, if pre-pregnancy is overweight or even obesity, then the weekly weight gain is recommended to control in the degree or 0.22kg to 0.28kg. Appropriate weight gain during pregnancy is conducive to obtaining a good pregnancy outcome, reduce gestational diabetes, the probability of the occurrence of macrosomia, should pay attention to weight management and monitoring during pregnancy, can be measured once a week under the guidance of obstetricians and moderate physical activity.