1. Department of Obstetrics and Gynecology, Naval Hospital Camp Pendleton, 200 Mercy Circle, Oceanside, California
2. Department of Obstetrics and Gynecology, Walter Reed National Military Medical Center, Bethesda, Maryland
3. Center for Health Services Research, Henry M. Jackson Foundation, Bethesda, Maryland
4. Department of Obstetrics and Gynecology, Wright-Patterson United States Air Force Medical Center, Dayton, Ohio
5. Center for Health Services Research, Uniformed Services University of the Health Sciences, Bethesda, Maryland
6. Department of Obstetrics and Gynecology, Uniformed Services University of the Health Sciences, Bethesda, Maryland