You should not have sex in the first trimester of pregnancy, because the gestational sac is not very stable at this time, and if you have sex, it may cause pre-eclampsia or embryo stop developing. In the last trimester of pregnancy also can not have sex, because at this time the pregnant woman’s abdomen is relatively large, if you have sex, may cause pressure on the fetus or cause premature rupture of the fetal membranes and fetal membranes, amnionitis, the impact on the fetus is very big. There is a risk of preterm labor and inflammation of the vagina, which can have an impact on delivery. During the 3-7 months of pregnancy, you can have sex, but when you have sex, you must be gentle and not too frequent to avoid the impact on the fetus.