1 Department of Ultrasound, West China Second University Hospital, Sichuan University, Chengdu, China; Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu, China.
2 Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu, China; Department of Obstetrics, West China Second University Hospital, Sichuan University, Chengdu, China.
3 Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu, China; Department of Reproductive Medicine, West China Second University Hospital, Sichuan University, Chengdu, China.
4 Department of Ultrasound, West China Second University Hospital, Sichuan University, Chengdu, China; Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu, China. Electronic address: luohongcd1969@126.com.