Affiliation: | (1) Departments of Medicine, Epidemiology, Obstetrics, Gynecology, and Reproductive Sciences, University of Pittsburgh, Center for Research on Health Care, 230 McKee Place, Suite 600, Pittsburgh, PA 15213, USA;(2) Division of Research, Kaiser Permanente Northern California, Oakland, CA, USA;(3) Department of Obstetrics and Gynecology, Southcentral Foundation, Anchorage, AK, USA;(4) Mid-Atlantic Permanente Research Institute, Rockville, MD, USA |