Neighbourhood Poverty Histories and Severe Maternal Morbidity Across California Census Tracts

Background Severe maternal morbidity (SMM) and its racial and ethnic inequities are the result of a mixture of risk factors ranging from clinical comorbidities to socio‐economic contexts. One under‐explored dimension is neighbourhood contexts. Objectives In order to understand the impact of neighbourhood contexts on SMM, this study investigates the relationship between a 20‐year history of neighbourhood poverty and SMM among 8.6 million births in California from 2000 to 2018 and assesses effect measure modification by race/ethnicity and nativity. Methods Data include hospital live births in California from 2000 to 2018 from the California Department of Public Health. The final sample for this study consisted of 8,632,436 live births. Mixed‐effects logistic regression models accounting for area‐level clustering were used to compare the odds of SMM across neighbourhood poverty histories, adjusting for sociodemographic and pregnancy‐related factors and comorbidities. Results The prevalence of SMM was 1.2%. In fully adjusted models, neighbourhoods with persistent high poverty had 32% higher odds of SMM (OR 1.32, 95% confidence interval [CI] 1.28, 1.37), and those with persistent moderate poverty had 9% higher odds (OR 1.09, 95% CI 1.06, 1.12), compared to neighbourhoods with a persistent low poverty history. The odds of SMM were also higher in neighbourhoods with increasing poverty; 23% higher for early increase (OR 1.23, 95% CI 1.19, 1.27) and 13% higher for late increase (OR 1.13, 95% CI 1.09, 1.16). In contrast, neighbourhoods with early decreasing poverty had 11% lower odds of SMM (OR 0.89, 95% CI 0.84, 0.94) compared to persistent lowpoverty neighbourhoods. Conclusions The findings indicate that persistent high poverty in neighbourhoods is associated with higher odds of SMM, independent of individual sociodemographic and clinical factors. The strongest associations were found among Asian, Hispanic, Pacific Islander and white birthing people. These results underscore the significance of neighbourhood poverty histories and their impact on maternal health.