The standard fetal weight in the 6th month of pregnancy is about 630-900g, and the normal placenta weight is about 1/6 of the fetal weight. However, amniotic fluid is usually not calculated by weight, but by checking the depth of amniotic fluid and amniotic fluid index to determine whether it is normal. The depth of amniotic fluid is about 2-8cm at 6 months of pregnancy, and the amniotic fluid index is 5-25cm. if the fetus is too big, pregnant women should pay attention to control diet, control blood sugar, don’t eat greasy food and sweet food, and should eat more vegetables and coarse grains. Ensure that nutrition is reasonable, comprehensive and balanced, and avoid over-nutrition. You can exercise appropriately, such as doing simple housework, walking, doing yoga for pregnant women, etc., to control weight gain. If you find that the fetus is smaller than the gestational week, you should be alert to the occurrence of intrauterine growth retardation. First of all, check the gestational week and infer the gestational week according to the ultrasound result in early pregnancy, sometimes the small fetus may be caused by the miscalculation of the gestational week. Secondly, if the fetus is 1-2 weeks smaller than the corresponding gestational week, it is considered to be caused by normal error. However, if the size of the fetus is smaller than the corresponding gestational week by more than 3 weeks, intrauterine growth retardation should be considered. Pregnant women should pay attention to strengthen nutrition, if necessary, intravenous fluids for supplementation to promote fetal growth.