1. Department of Obstetrics and Gynecology, Seoul National University College of Medicine, Seoul, Korea
2. Department of Obstetrics and Gynecology, Seoul National University Bundang Hospital, Gyeonggi-do, Korea
3. Perinatology Research Branch, NICHD/NIH/DHHS, Detroit, MI, USA
4. Department of Obstetrics and Gynecology, University of Michigan, Ann Arbor, MI, USA
5. Department of Epidemiology and Biostatistics, Michigan State University, East Lansing, MI, USA
6. Center for Molecular Medicine and Genetics, Wayne State University, Detroit, MI, USA
7. Detroit Medical Center, Detroit, MI, USA
8. Department of Obstetrics and Gynecology, Yonsei University College of Medicine, Seoul, Korea