As the "two-child" policy implementation, caesarean women's clinical pregnancy is a huge problem again, Especially the placenta planting abnormal disease is a serious threat to the maternal health and life. Through this research, the investigators can obtain relevant epidemiological data and provide objective data for the department of public health policy; Predicting an placenta abnormal planting early diagnosis model was constructed, it will fill the blank in this field, and high-risk groups in the early stages of pregnancy will be taken proper disposal, the related complications will be reduced to ensure the safety of maternal.

This study focus on four hands: (1) to investigate different types of gestational sac implantation for pregnancy in caesarean women of childbearing age;(2) to explore the relationship between abnormal placenta planting disease in middle-late pregnancy and the different types of scar pregnancy (3) to explore the the value of ultrasound and serological markers for early diagnosis of placenta planting disease from scar pregnancy; (4) to compare the end and the influence of health economy of different termination method on scar pregnancy.

Inclusion Criteria:

• Single pregnancies with once cesarean section history
• see a doctor before gestational 8 weeks in our study center
• will continue to pregnancy, high patient compliance

Exclusion Criteria:

• twins or multiple pregnancies
• hysteromyoma or adenomyoma stripping history
• history of intrauterine adhesions

pregnant women with scar uterus

There are 6 hospitals participated this study, we need get their agreement to share data.