1 Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Duke University, Ste. 205, 2608 Erwin Rd., Durham, NC 27705. Electronic address: Sd132@duke.edu.
2 Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Vanderbilt University, Nashville, TN.
3 Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Wake Forest University, Winston-Salem, NC.
4 Division of Population and Community Health, Department of Obstetrics and Gynecology, Duke University, Durham, NC.
5 Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Indiana University, Indianapolis, IN.
6 Division of Complex Family Planning, Department of Obstetrics and Gynecology, The University of New Mexico, Albuquerque, NM.