1. Key Laboratory of Birth Defects and Related Diseases of Women and Children of MOE, Department of Pediatrics, West China Second University Hospital, Sichuan University, Chengdu, Sichuan 610041, China.
2. Department of Postgraduate Students, West China Medical School of Sichuan University, Chengdu, Sichuan 610041, China.
3. Department of Obstetrics, West China Second University Hospital, Sichuan University, Chengdu, Sichuan 610041, China.
4. Department of Ultrasound, West China Second University Hospital, Sichuan University, Chengdu, Sichuan 610041, China.