1. Department of Epidemiology, University of North Carolina at Chapel Hill Gillings School of Global Public Health, Chapel Hill, NC, USA,
2. Department of Health, Zhuhai Maternity and Child Health Hospital, Zhuhai, Guangdong, China,
3. Department of Epidemiology and
4. Department of Health Policy and Management, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD, USA,
5. National Office for Maternal and Child Health Surveillance of China, West China Second Hospital, Sichuan University, Chengdu, Sichuan, China, and
6. National Center for Birth Defects Monitoring of China, West China Second Hospital, Sichuan University, Chengdu, Sichuan, China