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PLoS One. 2018 Feb 21;13(2):e0192523. doi: 10.1371/journal.pone.0192523. eCollection 2018.

Mapping integration of midwives across the United States: Impact on access, equity, and outcomes.

Author information

Birth Place Lab, Department of Family Practice, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada.
University of Sydney, School of Medicine, Sydney, Australia.
Maryland Population Research Center, University of Maryland, College Park, Maryland, United States of America.
School of Public Health, Boston University, Boston, Massachusetts, United States of America.
Law, Politics and Society, Drake University, Des Moines, Iowa, United States of America.
Department of Anthropology, Oregon State University College of Liberal Arts, Corvallis, Oregon, United States of America.
Department of Obstetrics and Gynecology, Geisel School of Medicine, Dartmouth University, Lebanon, New Hampshire, United States of America.
Health Administration and Policy, George Mason University, Fairfax, Virginia, United States of America.
Department of Midwifery, Yale School of Nursing, Orange, Connecticut, United States of America.



Our multidisciplinary team examined published regulatory data to inform a 50-state database describing the environment for midwifery practice and interprofessional collaboration. Items (110) detailed differences across jurisdictions in scope of practice, autonomy, governance, and prescriptive authority; as well as restrictions that can affect patient safety, quality, and access to maternity providers across birth settings. A nationwide survey of state regulatory experts (n = 92) verified the 'on the ground' relevance, importance, and realities of local interpretation of these state laws. Using a modified Delphi process, we selected 50/110 key items to include in a weighted, composite Midwifery Integration Scoring (MISS) system. Higher scores indicate greater integration of midwives across all settings. We ranked states by MISS scores; and, using reliable indicators in the CDC-Vital Statistics Database, we calculated correlation coefficients between MISS scores and maternal-newborn outcomes by state, as well as state density of midwives and place of birth. We conducted hierarchical linear regression analysis to control for confounding effects of race.


MISS scores ranged from lowest at 17 (North Carolina) to highest at 61 (Washington), out of 100 points. Higher MISS scores were associated with significantly higher rates of spontaneous vaginal delivery, vaginal birth after cesarean, and breastfeeding, and significantly lower rates of cesarean, preterm birth, low birth weight infants, and neonatal death. MISS scores also correlated with density of midwives and access to care across birth settings. Significant differences in newborn outcomes accounted for by MISS scores persisted after controlling for proportion of African American births in each state.


The MISS scoring system assesses the level of integration of midwives and evaluates regional access to high quality maternity care. In the United States, higher MISS Scores were associated with significantly higher rates of physiologic birth, less obstetric interventions, and fewer adverse neonatal outcomes.

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