1. Department of Maternal and Child Health and MOE (Ministry of Education) Key Lab of Environment and Health, School of Public Health, Tongji Medical College Huazhong University of Science and Technology Wuhan China
2. Maternity and Children Health Care Hospital of Luohu District Shenzhen China
3. Department of Epidemiology and Biostatistics, Arnold School of Public Health University of South Carolina Columbia SC 29208 USA