Chinese Academy of Medical Sciences & Peking Union Medical College (CAMS & PUMC) - Department of Obstetrics and Gynecology, Sichuan University - Chinese Evidence-Based Medicine Centre, Tufts University - Deparment of OBGYN, Central South University - Department of Obstetrics and Gynecology, Wuxi Maternal and Child Health Care Hospital - Department of Obstetrics and Gynecology, Maternal and Child Health Care Hospital Changsha - Department of Obstetrics and Gynecology, Southern Medical University - Department of Gynecology, Xinjiang Medical UniversityXinjiang Medical University - Department of Obstetrics and Gynecology, Government of the People's Republic of China - Department of Obstetrics and Gynecology, Shandong University - Department of Obstetrics and Gynecology, Guangzhou Medical University - Department of Obstetrics and Gynecology, People's Hospital of Xinjiang Autonomous Region - Department of Gynecology, Sichuan University - Key Laboratory of Birth Defects and Related Diseases of Women and Children of Ministry of Education, Klinik Tettnang - Department of Obstetrics and Gynecology, Kaohsiung Chang Gung Memorial Hospital, Yale University - Department of Biostatistics, Sichuan University - Chinese Evidence-Based Medicine Centre and Chinese Academy of Medical Sciences & Peking Union Medical College (CAMS & PUMC) - Department of Obstetrics and Gynecology