1 Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center, Dallas, TX.
2 Peter O'Donnell Jr. School of Public Health, University of Texas Southwestern Medical Center, Dallas, TX.
3 Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center, Dallas, TX; Parkland Health, Dallas, TX.
4 Parkland Health, Dallas, TX.
5 Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center, Dallas, TX; Parkland Health, Dallas, TX. Electronic address: DavidB.Nelson@UTSouthwestern.edu.