Sexual intercourse after pregnancy may cause contractions of the uterus, but generally minor contractions will not have an effect. If frequent contractions occur, they may cause miscarriage or premature delivery, so it is clinically forbidden to have intercourse during the first trimester and the last trimester of pregnancy, that is, the trimester before delivery, while sex is allowed in the middle of pregnancy. In the first trimester, that is, before 12 weeks of pregnancy, sexual intercourse may lead to miscarriage, while in the first trimester, sexual intercourse may cause contractions leading to preterm labor or early water breakage. Premature rupture of membranes is usually caused by infection, so sex is prohibited.