[1] Hanyang Univ Hosp, Dept Obstet & Gynecol, Seoul, South Korea
[2] Yonsei Univ, Dept Obstet & Gynecol, Gangnam Severance Hosp, Seoul 120749, South Korea
[3] Keimyung Univ, Dept Obstet & Gynecol, Dongsan Med Ctr, Taegu, South Korea
[4] Seoul Natl Univ Hosp, Dept Obstet & Gynecol, Seoul 110744, South Korea
[5] Sungkyunkwan Univ, Dept Obstet & Gynecol, Samsung Med Ctr, Seoul, South Korea
[6] Univ Ulsan, Dept Obstet & Gynecol, Asan Med Ctr, Seoul, South Korea
[7] Catholic Univ Korea, Dept Obstet & Gynecol, Seoul St Marys Hosp, Seoul, South Korea
[8] Chonnam Natl Univ Hosp, Dept Obstet & Gynecol, Kwangju, South Korea
[9] GlaxoSmithKline Biol, Wavre, Belgium