1. Beijing Key Laboratory for Genetics of Birth Defects, Center of Endocrinology, Genetics and Metabolism, Beijing Children's Hospital, The Capital Medical University, National Center for Children's Health, Beijing 100045, China.
2. Center of Clinical Epidemiology and Evidence-Based Medicine, Beijing Children's Hospital, Capital Medical University, National Center for Children's Health; Department of Epidemiology and Biostatistics, School of Public Health, Capital Medical University, Beijing 100045, China.