[1] Chungnam Natl Univ Hosp, Dept Obstet & Gynecol, Daejeon, South Korea
[2] Seoul Natl Univ, Bundang Hosp, Dept Obstet & Gynecol, Seongnam, South Korea
[3] CHA Univ, CHA Bundang Med Ctr, Dept Radiol, Seongnam, South Korea
[4] Seoul Natl Univ, Coll Med, Dept Obstet & Gynecol, Seoul, South Korea
[5] Seoul Natl Univ, Bundang Hosp, Coll Med, Dept Obstet & Gynecol, 82 Gumi Ro,173 Beon Gil, Seongnam Si, Gyeonggi Do 13620, South Korea