Reproductive Medical Center, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, China. Reproductive Medical Center, Beijing Chao Yang Hospital, Capital Medical University, Beijing, China. Health Examination Center, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, China. Department of Environmental Health Sciences, University at Albany, State University of New York, NY. Pediatric Department, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, China.