The risk factors of placenta praevia with placental implantation: 1, maternal age: age ≥ 35 years, progressive endothelial damage and meconium dysplasia are the high risk factors of placenta praevia with placental implantation. 2, endometrial damage, such as multiple abortions, scraping, intrauterine infection, too much childbirth, etc. can cause endometrial damage, especially after the endometrial basal layer is destroyed, the functional layer of the endometrium cannot be effectively repaired, and when another pregnancy occurs, it can easily lead to placental implantation. The number of miscarriages is generally considered to be a high risk factor if the number of miscarriages is ≥2. 4. other factors: twin pregnancies, smoking, etc.