At seventeen weeks of pregnancy, the lower edge of the placenta covers the inner mouth of the cervix, and if there is no vaginal bleeding, abdominal pain, etc., it generally does not require special treatment, and regular ultrasound review to understand the placenta. Seventeen weeks of pregnancy is the middle pregnancy, after this period due to the formation of the lower segment of the uterus, the disappearance of the cervical canal, the dilatation of the uterine opening and other factors, increasing the distance between the endocervical opening and the edge of the placenta, originally attached to the endocervical opening of the uterine placenta can be changed to a normal position of the placenta with the uterine body upward movement. Pregnant women with placenta previa in mid-gestation do not have vaginal bleeding, abdominal pain, etc., and generally do not need special treatment. Regular checkups should be conducted to review the position of the placenta margins. If the position of the placenta is still low after 28 weeks of pregnancy, placenta praevia should be considered as a possible cause of placenta praevia, so it is necessary to pay attention to daily rest, avoid excessive exertion and sex, pay attention to the vaginal bleeding, and consult a doctor in case of abnormality. Pregnant women should have prenatal checkups on time to clarify the condition of the fetus and the lower edge of the placenta, and go to the doctor in time if there is vaginal bleeding to avoid affecting the health of the mother and child.