1 Department of Obstetrics and Gynecology, Seoul National University Bundang Hospital, 82 Gumi- ro 173beon-gil, Bundang-gu, 13620, Seongnam, Republic of Korea.
2 Department of Obstetrics and Gynecology, Seoul National University College of Medicine, Seoul, Republic of Korea.
3 Department of Obstetrics and Gynecology, Seoul National University Bundang Hospital, 82 Gumi- ro 173beon-gil, Bundang-gu, 13620, Seongnam, Republic of Korea. blasto@snubh.org.
4 Department of Obstetrics and Gynecology, Seoul National University College of Medicine, Seoul, Republic of Korea. blasto@snubh.org.