1 Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Eastern Virginia Medical School, Norfolk, VA, USA.
2 Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA.
3 Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA.
4 Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.