1. Department of Obstetrics and Gynaecology, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, China
2. Department of Obstetrics and Gynecology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, China
3. Department of Obstetrics and Gynaecology, Maternal and Child Health Care of Shandong Province, Jinan, China
4. Laboratory of Placenta-Related Diseases, Key Laboratory of Birth Regulation and Control Technology of National Health and Family Planning Commission of China, Jinan, China