Generally contractions after sex in mid-pregnancy need to be observed for about 24 hours, but there can be individual differences. Early pregnancy due to embryonic development is not stable, this period is not to have sex, to avoid increasing the risk of miscarriage. Since the middle of pregnancy, due to the placenta has been formed, and the development of the fetus is also more stable, at this time can be appropriate to have sex. But when the contractions after sex, if not frequent, can be observed for about 24 hours when the general situation is good is safe. Sex during pregnancy should pay attention to the action can not be too rough, and can not be too frequent, can not be pressed to the abdomen of pregnant women. In the last three months of pregnancy should not have sex, to avoid increasing the risk of preterm labor and premature rupture of membranes. Since the mid-pregnancy, you should also increase your diet to meet the physiological needs of the fast-growing fetus.