1. Department of Gynecology, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang 310003, P.R. China
2. Department of Gynecology, Shulan Hospital, Hangzhou, Zhejiang 310003, P.R. China
3. Department of Obstetrics, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang 310003, P.R. China