[1] Cleveland Clin, Dept Obstet & Gynecol, Cleveland, OH 44195 USA
[2] Peking Univ, Shenzhen Hosp, Dept Obstet & Gynecol, Shenzhen, Peoples R China
[3] Northwestern Univ, Dept Prevent Med, Chicago, IL 60611 USA
[4] Cleveland Clin, Dept Anat Pathol, Cleveland, OH 44195 USA