1. Department of Gynecology, Central Hospital, Nanjing, China;
2. School of Medicine, South East University, Nanjing, China;
3. Department of Obstetrics and Gynecology, BenQ Medical Center, The Affilicated BenQ Hospital of Nanjing Medical University, Nanjing, China;
4. Department of Obstetrics and Gynecology, South East University Affiliated Zhongda Hospital, Nanjing, China;
5. Department of Epidemiology and Biostatistics, School of Public Health, South East University, Nanjing, China