1. Department of Obstetrics and Gynecology, University of Colorado Anschutz Medical Campus, Aurora, Colorado
2. Department of Obstetrics and Gynecology, University of Michigan Health, Ann Arbor, Michigan
3. Department of Anesthesiology, ANEX Anesthesia, Brookfield, Wisconsin
4. Department of Anesthesia, Vanderbilt University Medical Center, Nashville, Tennessee
5. Department of Obstetrics and Gynecology, Vanderbilt University Medical Center, Nashville, Tennessee