1. Center for Women's Reproductive Health University of Alabama at Birmingham Birmingham AL USA
2. Department of Obstetrics and Gynecology, Division of Maternal–Fetal Medicine University of Alabama at Birmingham Birmingham AL USA
3. Department of Obstetrics and Gynecology, Division of Maternal–Fetal Medicine University of North Carolina School of Medicine and University of North Carolina Health Care Chapel Hill NC USA
4. Department of Obstetrics and Gynecology, Division of Maternal–Fetal Medicine Wake Forest School of Medicine Winston Salem NC USA