1. National Center for Birth Defects Monitoring , West China Second University Hospital, Sichuan University , Chengdu, Sichuan , P.R. China
2. Department of Pediatrics , West China Second University Hospital, Sichuan University , Chengdu, Sichuan , P.R. China
3. Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education , Chengdu , P.R. China
4. Department of Pediatrics , West China Second University Hospital, Sichuan University , 20, Section 3, Ren Min South Road , Chengdu, Sichuan , P.R. China , Phone: 86-028-85501363, Fax: 86-028-85501386
5. National Center for Birth Defects Monitoring of China , West China Second University Hospital, Sichuan University , 17, Section 3, Ren Min South Road , Chengdu, Sichuan , P.R. China , Phone: 86-028-85501189, Fax: 86-028-85501386