1. National Center for Birth Defect Monitoring; West China Second Hospital; Chengdu China
2. Laboratory of Molecular Epidemiology for Birth Defects; West China Second Hospital; Chengdu China
3. Department of Obstetrics and Gynecology; Sichuan University; Chengdu China
4. Laboratory of Genetics; West China Second Hospital; Chengdu China
5. Department of Ultrasound; Maternal and Child Health Hospital of Shenzhen; Shenzhen China
6. Department of Ultrasound; Maternal and Child Health Hospital of Hubei; Wuhan China
7. Department of Obstetrics and Gynecology; Maternal and Child Health Hospital of Fujian; Fuzhou China