1. Key Laboratory of Women’s Reproductive Health of Zhejiang Province, Women’s Hospital, School of Medicine, Zhejiang University, Hangzhou, China
2. The Key Laboratory of Reproductive Genetics (Zhejiang University), Ministry of Education, School of Medicine, Zhejiang University, Hangzhou, China
3. Department of Obstetrics, Women’s Hospital, School of Medicine, Zhejiang University, Hangzhou, China
4. Department of Ultrasound, Women’s Hospital, School of Medicine, Zhejiang University, Hangzhou, China
5. Department of Obstetrics, Jinhua People’s Hospital, Jinhua, China