[1] Kyungpook Natl Univ, Chilgok Hosp, Sch Med, Dept Obstet & Gynecol, Daegu, South Korea
[2] Kyung Hee Univ, Sch Med, Dept Obstet & Gynecol, Seoul, South Korea
[3] Sungkyunkwan Univ, Samsung Med Ctr, Sch Med, Dept Obstet & Gynecol, 81 Irwon Ro, Seoul 06351, South Korea
[4] Dongguk Univ, Grad Sch Med, Dept Obstet & Gynecol, Goyang, South Korea
[5] Konkuk Univ, Med Ctr, Sch Med, Dept Obstet & Gynecol, Seoul, South Korea
[6] Yonsei Univ, Coll Med, Inst Womens Life Med Sci, Dept Obstet & Gynecol, Seoul, South Korea