What the evidence says
The clearest signal in this evidence set is a null result: across 11 observational studies conducted in OECD settings, higher midwifery workload shows no measured effect on neonatal mortality or major morbidity — Apgar scores, neonatal ward admission, resuscitation rates, cord pH, shoulder dystocia, and composite "healthy baby" outcomes were all unaffected, with only one contradictory (low-quality) study breaking the pattern. Workload does, however, decrease process-level responsiveness during emergencies: when midwife-to-labouring-women ratios were at least 1:1, emergency caesareans were more likely to reach the recommended decision-to-delivery window of under 30 minutes, and fewer women were transferred to theatre outside the 15-minute window — implying that below that ratio, delay in these two measures increases.
Workload also shows a maternal-side cost that the neonatal data does not: higher workload increases perineal trauma, with an increased risk of perineal tears and a decrease in intact-perineum rates. A single vignette-based study found higher workload associated with increased oxytocin administration during spontaneous labour, though this measured reported hypothetical practice rather than observed clinical behavior, and rests on one study.
The relationship between workload and caesarean birth rate is not uniform in these sources. One cohort study (Facchini) found a 19% increase in caesarean births comparing the highest to lowest workload 20th percentiles, but no association when workload was measured as a continuous variable — meaning the effect, where it exists, appears concentrated at workload extremes rather than scaling smoothly across the range.
Where a randomized comparison exists, the outcome depends on maternal risk status. Sandall et al. found lower workload produced greater benefit for low-risk women on both a "healthy baby" composite (p<0.009) and a "healthy mother" composite (p<0.001), but showed no measured effect on mode of birth or perineal outcomes among high-risk women — indicating that workload reduction's measured benefit here is contingent on risk category, and this study compared models of care rather than isolating a pure staffing variable.
Where the evidence splits
The effect of workload on caesarean birth rate is contested across the cited studies. Facchini found a 19% increase in caesareans at the highest workload extreme but no association when workload was treated as continuous; separately, Vanderlaan found the opposite direction, with higher staffing (i.e., lower workload) associated with lower caesarean rates; and several other studies found no association at all. The claims attribute part of this disagreement to inconsistent measurement of workload across studies — some use a ratio, some a dichotomous split, some an aggregate measure — but do not fully reconcile why Vanderlaan's direction diverges from Facchini's extreme-workload finding.
Thresholds and dose-response
Two thresholds are stated directly in the sources. First, a midwife-to-labouring-women ratio of at least 1:1 is the cutoff at which emergency caesareans become more likely to meet the 30-minute decision-to-delivery timeframe and theatre transfers become more likely to occur within 15 minutes; below that ratio, both measures are more likely to be delayed. Second, for caesarean birth rate, the effect is concentrated at workload extremes: comparing the highest to lowest workload 20th percentiles produced a 19% increase in caesareans, while no association appeared when workload was measured continuously — indicating the relationship is not linear across the full range of workload.