1. Department of Obstetrics and Gynecology, Brown University Warren Alpert Medical School, Providence, Rhode Island
2. Department of Obstetrics and Gynecology, University of South Florida, Tampa, Florida
3. Department of Obstetrics and Gynecology, Duke University School of Medicine, Durham, North Carolina
4. UCLA School of Medicine, Los Angeles, California
5. Center for Fetal Medicine and Women's Ultrasound, Los Angeles, California
6. Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco, San Francisco, California
7. Department of Obstetrics and Gynecology, Maternal and Child Health Research Center, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania