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