OBJECTIVE:
To quantify the extent to which rising rates of severe maternal morbidity (SMM) in the United States from 2016 to 2022 are attributable to increasing prevalence of maternal risk factors, including advanced maternal age, obesity, pregestational diabetes mellitus, gestational diabetes, chronic hypertension, and hypertensive disorders of pregnancy (HDP).
METHODS:
We conducted a retrospective cohort study using the Nationwide Readmissions Database from 2016 to 2022, representing more than 25 million weighted delivery hospitalizations. The primary outcome of SMM was identified with the Centers for Disease Control and Prevention’s 21-condition algorithm; a secondary outcome excluded transfusion to improve specificity. Temporal trends in SMM and maternal risk factors were assessed with the Cochran–Armitage test. To quantify the contribution of changes in risk factor prevalence to the overall increase in SMM, we applied a parametric g-computation–based decomposition comparing standardized risks in 2016 and 2022, including counterfactual scenarios in which the distribution of each risk factor was held at 2016 levels.
RESULTS:
Between 2016 and 2022, the prevalence of SMM increased from 1.5% to 2.2%, and nontransfusion SMM rose from 0.7% to 1.0% (both P<.001). The prevalence of HDP rose from 9.8% to 16.6%, chronic hypertension from 1.4% to 2.6%, and obesity from 9.7% to 15.4%. All maternal risk factors were independently associated with higher odds of SMM. Decomposition analysis showed that HDP accounted for 32.4% (95% CI, 31.2–33.7%) of the increase in SMM and 51.3% (95% CI, 48.5–54.9%) of the increase in nontransfusion SMM. Chronic hypertension and obesity also contributed meaningfully, whereas advanced maternal age and gestational diabetes accounted for a smaller share of the increase.
CONCLUSION:
The rise in SMM in the United States is partially attributable to the growing burden of chronic hypertension, HDP, and obesity. These findings highlight the urgent need for preventive interventions targeting cardiometabolic health before, during, and after pregnancy.