This study assessed and quantified the effect of quality of care on death preventability, independent of social and biological variables. One hundred and eighty-one avoidable perinatal deaths (cases) were compared to 341 non-avoidable ones (controls). Judgement criteria on death preventability were based predominantly on compliance with explicit hospital medical care standards, determined by peer review. The overall perinatal mortality rate was 24.8 per 1000 births and could be reduced by 35% if all avoidable perinatal deaths were prevented. Sixteen per cent of the deaths presented structural and 31.2% process deficiencies; both predominated among avoidable perinatal deaths (35.4% vs 5.3%, p < 0.000; and 79.3% vs 5.9%, p < 0.000, respectively). Structural deficiencies increased the risk of an avoidable perinatal death eleven-fold (95% confidence interval (CI) 4.1, 26.9; p < 0.001) and process deficiencies eighty-eightfold (95% CI 37.2, 204.5, p < 0.001), after controlling for confounders. The strength of the association between quality of care and preventable perinatal mortality was estimated.