Pregnant women sleeping on their stomachs, early pregnancy in the middle or late pregnancy may lead to miscarriage, preterm labor or intrauterine distress, etc., in the early stages of pregnancy on the fetus has less impact. Pregnant women in early pregnancy, because the abdomen has not yet bulged or bulge amplitude is small, the uterus is still in the pelvic cavity, at this time sleep on the stomach on the fetus is usually less impact. For pregnant women in the middle or late pregnancy, sleeping on the stomach will cause serious pressure on the uterus, some pregnant women may produce contractions, which may lead to preterm labor or miscarriage. Prolonged compression may also lead to uterine compression of the inferior vena cava, resulting in poor blood return, and in severe cases, intrauterine distress of the fetus. It is recommended that pregnant women do not take the position of sleeping on their stomachs after pregnancy, especially in the middle and late stages of pregnancy, it is best to lie on the left side.