1. Division of Birth Cohort Study, and
2. Department of Health Care, Guangzhou Women and Children’s Medical Center, Guangzhou Medical University, Guangzhou, China
3. Guangzhou Women and Children’s Health Information Center, Guangzhou, China
4. Guangdong Provincial Institute of Public Health, Guangdong Provincial Center for Disease Control and Prevention, Guangzhou, China
5. School of Public Health, Key Lab of Public Health Safety of the Ministry of Education, Fudan University, China
6. Center for Prevention of Preterm Birth, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, USA