[1] Ewha Womans Univ, Dept Prevent Med, Coll Med, Seoul 158710, South Korea
[2] Ewha Womans Univ, Dept Obstet & Gynecol, Seoul, South Korea
[3] Ewha Womans Univ, Med Res Inst, Seoul, South Korea
[4] Ewha Womans Univ, Dept Anat, Seoul, South Korea
[5] Ewha Womans Univ, Dept Pediat, Seoul, South Korea
[6] Seoul Natl Univ, Dept Prevent Med, Seoul, South Korea