[1] China Meitan Gen Hosp, Dept Obstet & Gynaecol, 29 Xibahe Nanli, Beijing 100028, Peoples R China
[2] China Acad Chinese Med Sci, Wangjing Hosp, Beijing, Peoples R China
[3] Peking Univ, Sch Oncol, Canc Hosp, Dept Radiat Oncol, Beijing 100871, Peoples R China