1. Department of Obstetrics and Gynecology, Seoul National University College of Medicine, Seoul, Korea,
2. Department of Biochemistry and Molecular Biology, Hanyang University College of Medicine, Seoul, Korea
3. Department of Obstetrics, Gynecology, and Reproductive Sciences, Yale University School of Medicine, New Haven, Conneticut, U.S.A.
4. Department of Obstetrics and Gynecology, Seoul National University College of Medicine, Seoul, Korea