1. National Center for Birth Defects Monitoring, West China Second University Hospital, Sichuan University, Chengdu, China;
2. Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, West China Second University Hospital, Sichuan University, Chengdu, China;
3. Department of Obstetric and Gynecologic, West China Second University Hospital, Sichuan University, Chengdu, China