1 Department of Obstetrics and Gynecology, The George Washington University School of Medicine and Health Sciences, Washington, DC, USA.
2 The George Washington University School of Medicine and Health Sciences, Washington, DC, USA.
3 Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, University of North Carolina School of Medicine, Chapel Hill, NC, USA.
4 Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, The George Washington School of Medicine and Health Sciences, Washington, DC, USA.