The fourth month of pregnancy is the middle of pregnancy, at this time appropriate intercourse is possible, the situation of the baby in the middle of pregnancy, has been more stable, basically will not appear pre-miscarriage and other symptoms. It is advisable not to have intercourse during the first and second trimesters of pregnancy. The placenta is unstable in the early stages of pregnancy, and it is likely that there will be pre-eclampsia, and if you have sex in the later stages of pregnancy, you may stimulate the fetus to have symptoms of pre-eclampsia, so it is okay to have sex in the middle of pregnancy properly. But pay attention to grasp the time, do not frequent sex, each time the same room, do not over force, the time is best not too long, so as not to affect the health of pregnant women.