1. From the National Reference Laboratory on Reproductive and Child Health, Ministry of Health and National Center for Maternal and Infant Health, Peking University Health Science Center, Beijing, China (LH, ZL, J-HZ, LZ, and SL); the National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, Atlanta, GA (Q-HY, DJH, JDE, and RJB); the Food Science an