[1] Chinese Acad Med Sci, Dept Gynecol & Obstet, Peking Union Med Coll Hosp, Beijing 100730, Peoples R China
[2] Chinese Acad Med Sci, Peking Union Med Coll, Beijing 100730, Peoples R China
[3] Chinese Acad Med Sci, Inst Basic Med Sci, Dept Epidemiol & Stat, Beijing 100730, Peoples R China
[4] Peking Union Med Coll, Sch Basic Med, Beijing 100021, Peoples R China
[5] Maternal & Child Hlth Hosp Shanxi Prov, Dept Gynecol & Obstet, Taiyuan, Shanxi, Peoples R China
[6] Maternal & Child Hlth Hosp Wuxi, Dept Gynecol & Obstet, Wuxi, Jiangsu, Peoples R China
[7] Gansu Prov Matern & Child Care Hosp, Dept Gynecol & Obstet, Lanzhou, Gansu, Peoples R China
[8] Maternal & Child Hlth Hosp Foshan, Dept Gynecol & Obstet, Foshan, Guangdong, Peoples R China