Perinatal outcomes of midwife-led care, stratified by medical risk: a retrospective cohort study from British Columbia (2008–2018)

BACKGROUND: Anecdotal evidence suggests that the profile of midwifery clients in British Columbia has changed over the past 20 years and that midwives are increasingly caring for clients with moderate to high medical risk. We sought to compare perinatal outcomes with a registered midwife as the most responsible provider (MRP) versus outcomes among clients with physicians as their MRP across medical risk strata. METHODS: This retrospective cohort study (2008–2018) used data from the BC Perinatal Data Registry. We included all births that had a family physician, obstetrician or midwife listed as the MRP (n = 425 056) and stratified the analysis by pregnancy risk status (low, moderate or high) according to an adapted perinatal risk scoring system. We estimated differences in outcomes between MRP groups by calculating adjusted absolute and relative risks. RESULTS: The adjusted absolute and relative risks of adverse neonatal outcomes were consistently lower among those who chose midwifery care across medical risk strata, compared with clients who had a physician as MRP. Midwifery clients experienced higher rates of spontaneous vaginal births, vaginal births after cesarean delivery and breastfeeding initiation, and lower rates of cesarean deliveries and instrumental births, with no increase in adverse neonatal outcomes. We observed an increased risk of oxytocin induction among high-risk birthers with a midwife versus an obstetrician as MRP. INTERPRETATION: Our findings suggest that compared with other providers in BC, midwives provide safe primary care for clients with varied levels of medical risk. Future research might examine how different practice and remuneration models affect clinical outcomes, client and provider experiences, and costs to the health care system.