1. Department of Obstetrics and Gynaecology Shandong Provincial Hospital Shandong University Jinan Shandong China
2. Key Laboratory of Birth Regulation and Control Technology of National Health Commission of China Shandong Provincial Maternal and Child Health Care Hospital Jinan Shandong China
3. Department of General Surgery Qilu Hospital of Shandong University Jinan China
4. Department of Obstetrics and Gynaecology Maternal and Child Health Care Hospital of Shandong Provincial Jinan Shandong China