1. Department of Ultrasound; Shenzhen Maternity & Child Healthcare Hospital, Affiliated to Southern Medical University; Shenzhen China
2. Department of Obstetrics and Gynecology; Danbury Hospital; Danbury CT
3. Department of Obstetrics and Gynecology; Shenzhen Maternity & Child Healthcare Hospital, Affiliated to Southern Medical University; Shenzhen China
4. Department of Obstetrics and Gynecology; Tufts University School of Medicine; Boston MA
5. Department of Ultrasound; Guangxi Maternity and Child Healthcare Hospital; Nanning China
6. National Center for Birth Defects Monitoring; West China Second University Hospital, Sichuan University; Chengdu Sichuan China