During pregnancy, if coitus without contraception leads to sperm entering the vagina, there is no adverse effect on the baby, because the sperm will be discharged into the posterior fornix of the vagina, and the baby in the uterine cavity is protected by amniotic fluid, the amniotic cavity is closed, and the cervical os is closed, the cervical os also has cervical mucus plugs to play a role in protecting, so sperm will not enter the uterine cavity to affect the baby. But coitus should pay attention to the action gently, avoid rough action so as not to cause rupture of the amniotic membrane, may cause uterine infection, in addition in the first trimester of pregnancy should pay attention to avoid coitus, because coitus will stimulate the emergence of uterine contraction, which is prone to preeclampsia, and in the second trimester of pregnancy, the uterus increases, the pressure of the uterine cavity is elevated, coitus may also appear uterine contraction of the symptoms of preterm labor, so this time period should also be The first three months of pregnancy, the uterus is enlarged, the pressure of the uterine cavity rises, coitus may also have contractions and symptoms of premature labor, so this time period should also be careful not to coitus.