The fetal weight at 31 weeks of pregnancy is mostly 1.5-2.0kg, which is 3-4 pounds. The weight of the fetus varies from one pregnant woman to another. If the fetus is light or heavy, it is considered to be related to the mother’s own body size and nutritional intake, so it can be reviewed regularly and the nutritional intake can be adjusted according to the doctor’s prescription to ensure the healthy development of the fetus and normal delivery at the later stage, so as to avoid malnutrition and developmental delay of the fetus, as well as difficult delivery due to the large fetus caused by excess nutrition. If the fetus is too light or too heavy, consider whether there is fetal malformation or developmental abnormality, etc., and promptly check and treat it. At 31 weeks of pregnancy, the fetal development is complete, the skin is dark red, the surface is covered with fetal fat, the limbs are moving well, the lungs and digestive system are basically perfect, there are respiratory movements, the fetus needs more nutrition at this time, the pregnant woman can follow the doctor’s advice, combined with their own situation appropriate nutrition, pay attention to supplement calcium, iron. In addition, we should pay attention to other data of the fetus, such as biparietal diameter, length, femur length, abdominal circumference, etc., to determine whether the fetus is developing normally. In conclusion, the weight of the fetus may vary depending on the physical condition of the pregnant woman, so pay attention to regular maternity checkups and good personal health care.