Capital Medical University - Department of Central Laboratory, Peking University, Peking University, Peking University, Peking University - Center for Reproductive Medicine, Peking University, Peking University - Department of Epidemiology and Biostatistics, Peking University - Institute of Reproductive and Child Health, Peking University, China Medical University - Key Laboratory of Health Ministry for Congenital Malformation, China Medical University - Department of Ultrasound and Peking University