1. Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of North Carolina School of Medicine, Chapel Hill, NC, USA
2. Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Columbia University Medical Center, New York, NY, USA
3. Division of Neonatology, Department of Pediatrics, University of North Carolina School of Medicine, Chapel Hill, NC, USA