Sex during pregnancy is related to miscarriage and preterm delivery, but it is not the direct cause of miscarriage and preterm delivery, but only a precipitating factor. If there are no abnormalities in the indicators of pregnant women and fetuses, the chances of miscarriage or preterm delivery caused by moderate sex life are very small. On the contrary, choosing the right position and paying attention to the relevant matters (mastering the appropriate frequency, strength, duration, etc.) can also help pregnant women to maintain a relaxed state of mind, reduce pregnancy discomfort and enhance the couple’s relationship. In general, the number of intercourse should be reduced in early pregnancy and late pregnancy, while the number of intercourse can be increased in mid-pregnancy because the early pregnancy reaction disappears and the abdomen is smaller, which is the most relaxed stage during the whole pregnancy. Of course, it is recommended to strictly avoid sexual intercourse if the following conditions exist: unexplained vaginal bleeding, previous history of miscarriage or preterm delivery, current risk of miscarriage or preterm delivery, low placental status or placenta praevia, cervical insufficiency, hypertension during pregnancy, twin or multiple pregnancies, history of cesarean section or myomectomy, and inflammation of the reproductive tract on both sides. As mentioned earlier, sex during pregnancy should be moderate: specifically, the number of intercourse should be controlled, the duration of each intercourse should be short, shallow penetration and light movements, and the specific degree of control should be inconclusive, subject to the comfort of the pregnant woman; secondly, special attention should be paid to hygiene before and after intercourse, and both parties should wash their hands and external genitalia to reduce the risk of infection; in addition, special attention should be paid to avoid blowing during oral sex, as the air entering the vagina can be used to prevent the pregnancy. In addition, special attention should be paid to avoid blowing air during oral sex, because the air entering the vagina may cause air embolism if it accidentally enters the blood vessels, and in serious cases, pulmonary embolism in pregnant women, which is very dangerous.