1. Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Warren Alpert Medical School of Brown University, Providence, Rhode Island
2. Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Vanderbilt University Medical Center, Nashville, Tennessee
3. Division of Maternal Foetal Medicine, Department of Obstetrics and Gynecology, Newark Beth Israel Medical Centre, Newark, New Jersey
4. Department of Obstetrics and Gynecology, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, Pennsylvania