1. Division of Birth Cohort Study, Guangzhou Women and Children's Medical Center Guangzhou Medical University Guangzhou China
2. Department of Women's Health, Provincial Key Clinical Specialty of Woman and Child Health, Guangzhou Women and Children's Medical Center Guangzhou Medical University Guangdong China
3. Provincial Clinical Research Center for Child Health Guangdong China
4. Department of Obstetrics and Gynaecology The Chinese University of Hong Kong Hong Kong China
5. Nuffield Department of Women's and Reproductive Health University of Oxford Oxford UK