[1] Univ Ulsan, Coll Med, Asan Med Ctr, Dept Obstet & Gynecol, Seoul, South Korea
[2] Seoul Natl Univ, Seoul Metropolitan Govt Seoul Natl Univ, Coll Med, Boramae Med Ctr,Dept Obstet & Gynecol, 20 Boramae Ro 5-Gil, Seoul 07061, South Korea
[3] Kyungpook Natl Univ, Kyungpook Natl Univ Med Ctr, Sch Med, Dept Obstet & Gynecol, Daegu, South Korea
[4] Seoul Natl Univ, Seoul Natl Univ Bundang Hosp, Coll Med, Dept Obstet & Gynecol, Seongnam, South Korea
[5] Cathol Univ Korea, St Vincents Hosp, Coll Med, Dept Obstet & Gynecol, Suwon, South Korea
[6] Hanyang Univ, Med Ctr, Dept Obstet & Gynecol, Seoul, South Korea
[7] CHA Univ, CHA Gangnam Med Ctr, Dept Obstet & Gynecol, Seoul, South Korea
[8] Keimyung Univ, Sch Med, Dept Obstet & Gynecol, Daegu, South Korea
[9] Ewha Womans Univ, Sch Med, Dept Obstet & Gynecol, Seoul, South Korea
[10] Cathol Univ Korea, Seoul St Marys Hosp, Coll Med, Dept Obstet & Gynecol, Seoul, South Korea
[11] Dankook Univ, Cheil Gen Hosp, Dept Obstet & Gynecol, Seoul, South Korea
[12] Dankook Univ, Womens Healthcare Ctr, Seoul, South Korea
[13] Yonsei Univ, Gangnam Severance Hosp, Coll Med, Dept Obstet & Gynecol, Seoul, South Korea
[14] Inje Univ, Sanggye Paik Hosp, Dept Obstet & Gynecol, Seoul, South Korea
[15] Ajou Univ, Sch Med, Dept Obstet & Gynecol, Suwon, South Korea
[16] Korea Univ, Coll Med, Dept Obstet & Gynecol, Seoul, South Korea
[17] Sungkyunkwan Univ, Samsung Med Ctr, Sch Med, Dept Obstet & Gynecol, Seoul, South Korea
[18] Seoul Natl Univ Hosp, Dept Obstet & Gynecol, Seoul, South Korea