Shihua Bao1, Hong Liao2, Wen Shuai3, Lei Wang4, Jingjing Hu4. 1. Department of Gynecology, Shanghai First Maternity and Infant Hospital, Tongji University School of Medicine, Shanghai 201204, China. 2. Clinical and Translational Research Center, Shanghai First Maternity and Infant Hospital, Tongji University School of Medicine, Shanghai 201204, China. 3. Department of Gynecology, Shanghai First Maternity and Infant Hospital, Tongji University School of Medicine, Shanghai 201204, China. Email: 1287899041@qq.com. 4. Department of Ultrasound, Shanghai First Maternity and Infant Hospital, Tongji University School of Medicine, Shanghai 201204, China.