[1] Beijing Union Med Coll Hosp, Dept Obstet & Gynecol, Peking Union Med Coll, Beijing 100730, Peoples R China
[2] Zhejiang Univ, Dept Gynecol, Womens Hosp, Sch Med, Hangzhou 310006, Zhejiang, Peoples R China
[3] Huazhong Univ Sci & Technol, Tongji Med Coll, Dept Obstet & Gynecol, Wuhan 430030, Hubei, Peoples R China