AbstractIntroductionSevere maternal morbidity (SMM) is rising globally. Assessing SMM is an important quality measure. This study aimed to examine SMM in a national cohort in New Zealand.Material and methodsThis is a national retrospective review of pregnant or postpartum women admitted to an Intensive Care Unit or High Dependency Unit during pregnancy or recent postpartum. Outcomes were rates of SMM and assessment of potential preventability. Preventability was defined as any action on the part of the provider, system or patient that may have contributed to progression to more severe morbidity, and was assessed by a multidisciplinary review team.ResultsSevere maternal morbidity was 6.2 per 1000 deliveries (95% confidence interval 5.7‐6.8) with higher rates for Pacific, Indian and other Asian racial groups. Major blood loss (39.4%), preeclampsia‐associated conditions (23.3%) and severe sepsis (14.1%) were the most common causes of SMM. Potential preventability was highest with sepsis cases (56%) followed by preeclampsia and major blood loss (34.3% and 30.9%). Of these cases, only 36.4% were managed appropriately as determined by multidisciplinary review. Provider factors such as inappropriate diagnosis, delay or failure to recognize high risk were the most common factors associated with potential preventability of SMM. Pacific Island women had over twice the rate of preventable morbidity (relative risk 2.48, 95% confidence interval 1.28–4.79).ConclusionsMultidisciplinary external anonymized review of SMM showed that over a third of cases were potentially preventable, being due to substandard provider care with increased preventability rates for racial/ethnic minority women. Monitoring country rates of SMM and implementing case reviews to assess potential preventability are appropriate quality improvement measures and external review of anonymized cases may reduce racial profiling to inform unbiased appropriate interventions and resource allocation to help prevent these severe events.