Antenatal Midwifery Care and Reduced Prevalence of Small-for-Gestational-Age Birth and Other Adverse Infant Birth Outcomes for Women of Low Socioeconomic Position: A Population Based Cohort Study Comparing Midwifery and Physician-Led Models of Care

Purpose: The purpose of this research was to determine if antenatal midwifery care was associated with reduced odds of small-for-gestational-age (SGA) birth, preterm birth (PTB), large-for-gestational-age (LGA) birth, Apgar score less than seven at one minute (low Apgar score), newborn extended length of hospital stay (ELOS), or low birth weight (LBW) compared to antenatal care provided by general practitioners (GPs) or obstetricians (OBs) for women with low socioeconomic position (SEP). Methods: Prior to the main analysis, I conducted a systematic scoping review investigating if, over the last 25 years in high resource countries, midwives’ clients of low SEP were at more or less risk of adverse infant birth outcomes compared to physicians’ patients. The primary analysis was a population level, retrospective cohort study restricted to women with low to moderate risk pregnancy. Women were included if they had been residing in British Columbia, Canada, had singleton births between January 1, 2005 to December 31, 2012, no more than two provider-types involved in care, did not have registered Indian Status, and received Medical Services Plan (MSP) premium subsidy assistance (n=57,872). Generalized estimating equation logistic regression models were used to control for confounding. Results: For patients receiving antenatal midwifery vs. physician care, adjusted odds of SGA birth were reduced (MW vs. GP: OR 0.73, 95% CI: 0.63-0.84; MW vs. OB: OR 0.60, 95% CI: 0.51-0.70), as were odds of preterm birth (MW vs. GP: OR 0.74, 95% CI: 0.63-0.86; MW vs. OB: OR 0.53, 95% CI: 0.45-0.62). Odds of LGA birth were higher for those in the care of midwives vs. physicians (MW vs. GP: OR 1.28, 95% CI: 1.16-1.40; MW vs. OB: OR 1.46, 95% CI: 1.30-1.63). Odds of low Apgar score were only significantly reduced for midwives’ vs. GPs’ patients (OR 0.85, 95% CI: 0.77-0.95). Odds of newborn ELOS were reduced among midwives’ vs. physicians’ patients (MW vs. GP: OR 0.65, 95% CI: 0.57-0.74; MW vs. OB: OR 0.56, 95% CI: 0.49-0.65). Odds of LBW were reduced for patients receiving antenatal midwifery vs. physician care (MW vs. GP: OR 0.66, 95% CI: 0.53-0.82; MW vs. OB: OR 0.43, 95% CI: 0.34-0.54). Midwifery vs. physician patients with substance use and/or mental health conditions, and substance using teen mothers, had even lower odds of some adverse infant outcomes. A second analysis showed a reduction in odds of PTB for midwives’ vs. GPs’ patients of transient low SEP (OR 0.51, 95% CI: 0.37-0.71), but no difference in odds for patients of chronic low SEP. Conclusion: Changes in physicians’ antenatal models of practice, to align with the midwifery model, may improve newborn outcomes for vulnerable women at a population level. Midwifery care should be equally available and accessible to all women, using intensive outreach for women of low SEP if necessary, to promote the highest level of health for all infants