Factors associated with maternal death from direct pregnancy complications: a UK national case–control study

OBJECTIVE: To investigate the factors associated with maternal death from direct pregnancy complications in the UK. DESIGN: Unmatched case–control analysis. SETTING: All hospitals caring for pregnant women in the UK. POPULATION: A total of 135 women who died (cases) between 2009 and 2012 from eclampsia, pulmonary embolism, severe sepsis, amniotic fluid embolism, and peripartum haemorrhage, using data from the Confidential Enquiry into Maternal Death, and another 1661 women who survived severe complications (controls) caused by these conditions (2005–2013), using data from the UK Obstetric Surveillance System. METHODS: Multivariable regression analyses were undertaken to identify the factors that were associated with maternal deaths and to estimate the additive odds associated with the presence of one or more of these factors. MAIN OUTCOME MEASURES: Odds ratios associated with maternal death and population-attributable fractions, with 95% confidence intervals. Incremental risk of death associated with the factors using a ‘risk factors’ score. RESULTS: Six factors were independently associated with maternal death: inadequate use of antenatal care (adjusted odds ratio, aOR 15.87, 95% CI 6.73–37.41); substance misuse (aOR 10.16, 95% CI 1.81–57.04); medical comorbidities (aOR 4.82, 95% CI 3.14–7.40); previous pregnancy problems (aOR 2.21, 95% CI 1.34–3.62); hypertensive disorders of pregnancy (aOR 2.44, 95% CI 1.31–4.52); and Indian ethnicity (aOR 2.70, 95% CI 1.14–6.43). Of the increased risk associated with maternal death, 70% (95% CI 66–73%) could be attributed to these factors. Odds associated with maternal death increased by three and a half times per unit increase in the ‘risk factor’ score (aOR 3.59, 95% CI 2.83–4.56). CONCLUSIONS: This study shows that medical comorbidities are importantly associated with direct (obstetric) deaths. Further studies are required to understand whether specific aspects of care could be improved to reduce maternal deaths among women with medical comorbidities in the UK.