1. Department of Ultrasound, West China Second University Hospital Sichuan University Chengdu Sichuan China
2. Key Laboratory of Birth Defects and Related Diseases of Women and Children, Ministry of Education Sichuan University Chengdu Sichuan China
3. Department of Gynaecology and Obstetrics, West China Second University Hospital Sichuan University Chengdu Sichuan China