The lower edge of the placenta covers the inner cervical opening in the third month of pregnancy, which is a state of low placentation. In the third trimester, the placenta itself usually occupies half of the uterine wall, so there is more chance of the placenta being close to or covering the endocervix. In the middle and late stages of pregnancy, the placenta occupies 1/3 or 1/4 of the entire uterine wall, and the formation and extension of the lower uterine segment increases the distance between the inner cervical opening and the edge of the placenta, and most of the placenta can become normally positioned with the upward movement of the uterine body. Therefore, when the lower edge of the placenta covers the inner cervical opening in the third month of pregnancy, in principle, it is not called placenta previa, but rather placenta hypoplasia. At this time, if there are no clinical symptoms and no abnormal vaginal bleeding, we can observe and review the ultrasound regularly. If the placenta still covers the endocervix after 28 weeks, placenta praevia is diagnosed and treated according to the principles of treatment of placenta praevia. If the pregnancy is less than 37 weeks, the fetus is alive, the pregnant woman is in good condition, and the vaginal bleeding is low, it is feasible to prolong the pregnancy for as long as possible to improve the survival rate of the fetus without emergency delivery. In case of recurrent bleeding or heavy vaginal bleeding, it is necessary to seek medical attention as soon as possible and take appropriate treatment, including suppression of contractions, control of bleeding, correction of anemia and prevention of infection. In addition, pregnant women should take rest, avoid straining, and avoid sexual intercourse during pregnancy. If the diagnosis of placenta praevia is confirmed, you should rest in bed absolutely to prevent bleeding after activity and go to the hospital if you feel unwell.