The lower edge of the placenta reaching the endocervical os is less dangerous when found in early pregnancy, and has a certain risk when found after 28 weeks of pregnancy. Normal placental position is located in the anterior wall, posterior wall, lateral wall, bottom of the uterus, the lower edge of the placenta is more than 7cm from the cervical os, the lower edge of the placenta reaches the cervical os and the distance from the cervical os is less than 7cm, the placenta is hypoplastic before the 28th week of pregnancy, and the placenta is placenta praevia after the 28th week of pregnancy. The lower edge of the placenta reaches the endocervical os before 28 weeks of pregnancy, with the increase of pregnancy weeks and the gradual development of the fetus, the placenta may move up to the normal position, the earlier the discovery of the placenta, the higher the possibility of rising, the placenta rises with the growing uterus no longer covers the endocervical os, and the risk to the fetus and the pregnant woman is relatively small. Placenta praevia can be diagnosed after 28 weeks of pregnancy when the lower edge of the placenta reaches the endocervical os, which is dangerous because contractions can cause the placental vessels to rupture and cause vaginal bleeding, which can increase the chance of preterm labor. The lower edge of the placenta reaching the endocervix can block the descent of the fetal head and lead to fetal malposition, which increases the risk of a normal delivery, and a cesarean section is usually recommended. Pregnant women with a placenta with a lower edge of the placenta reaching the endocervical os should undergo regular checkups and have any abnormalities treated in a timely manner.