Generally speaking, after the middle of pregnancy, that is, after the third month of pregnancy, you can have sex appropriately. Because the placenta has been formed in this period, the condition of the fetus is more stable, appropriate coitus will not cause more serious effects. But early pregnancy, late pregnancy should be prohibited sex, so as not to cause adverse effects. The specific reasons are as follows: 1, early pregnancy: because early pregnancy that is, before 12 weeks, due to the female endocrine influence and produce early pregnancy reaction, coupled with the consideration of the safety of the fetus in the abdomen, should reduce the requirements and frequency of coitus. And at this time the uterus is more sensitive, the placenta has not yet matured, the placenta and the uterine wall connection is not yet close, followed by the prevention of miscarriage of progesterone secretion is insufficient to give strong protection to the fetus, coitus may lead to preeclampsia or even miscarriage; 2, late pregnancy: at this time due to the uterus grows too fast resulting in the fall of the amniotic sac, coitus is easy to cause premature rupture of the membranes, which may cause infections, prolapse of umbilical cord and preterm delivery, fetal The danger of premature labor, fetal distress and so on, so to avoid coitus. Although the middle of pregnancy can be appropriate coitus, but in order to avoid causing adverse effects to the fetus, coitus need to pay attention to related matters. For example, pay attention not to take the position of pressure to the pregnant woman; pay attention to movements gently, not rough; pay attention to both sides of the hygiene and cleanliness, to avoid infection; it is recommended to use a condom, so as not to stimulate the fetus.