1. Department of Obstetrics and Gynecology; West China Second University Hospital, Sichuan University; Chengdu China
2. Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University); Ministry of Education; Chengdu China
3. Reproductive Endocrinology and Regulation Laboratory; West China Second University Hospital, Sichuan University; Chengdu China
4. Department of Obstetrics and Gynecology; Affiliated Hospital of Guilin Medical University; Guilin China
5. Chinese Clinical Trial Registry, Chinese Ethics Committee of Registering Clinical Trials; West China Hospital, Sichuan University; Chengdu China
6. Mother and Baby Center, School of Medicine and Public Health; The University of Newcastle; New Castle China
7. Cochrane China; West China Hospital, Sichuan University; Chengdu China