1. National Office for Maternal and Child Health Surveillance of China, Department of Gynecology and Obstetrics, West China Second University Hospital, Sichuan University, Chengdu, Sichuan, China,
2. Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu, Sichuan, China,
3. Health and Nutrition & Water, Sanitation and Hygiene, UNICEF China, Beijing, China, and
4. Health Section, UNICEF Regional Office for South Asia, Kathmandu, Nepal