Assessing the Role of Cardiac Disease in Severe Maternal Morbidity: A Population-Based Cohort Study

To evaluate whether people with cardiac disease were at increased odds of nontransfusion severe maternal morbidity (SMM) and specific types of SMM during delivery hospitalization through 42 days postpartum compared with those without cardiac disease.

We conducted a retrospective cohort study using linked birth certificate and hospital discharge data. The study included singleton deliveries at 20-44 weeks of gestation in California from 2007 to 2020. People with cardiac disease before delivery hospitalization were identified with diagnosis codes. The presence of nontransfusion SMM from delivery through 42 days postpartum was chosen as the primary outcome because blood transfusion alone without other SMM occurs often during delivery hospitalization and is nonspecific. Odds of SMM were examined by type in logistic regression models adjusted for confounding factors. Timing of nontransfusion SMM events (during delivery or postpartum) was also examined.

Of 5,848,486 eligible births, 30,359 (0.5%) were to individuals with preexisting cardiac disease. People with cardiac disease had significantly increased odds of nontransfusion SMM (9.1% vs 0.8%, adjusted odds ratio [AOR] 6.88, 95% CI, 6.57-7.19) and SMM with transfusion (11.5% vs 1.7%, AOR 4.69, 95% CI, 4.50-4.88). Odds of cardiac SMM (AOR 53.49, 95% CI, 49.82-57.40) and pulmonary SMM (AOR 11.79, 95% CI, 10.84-12.81) were especially higher in those with cardiac disease, although all types were increased. Nontransfusion SMM events were more likely to occur during delivery hospitalization (compared with postpartum) in people with cardiac disease compared with those without cardiac disease (91.9% vs 75.5%, P<.01).

People with cardiac disease have significantly higher odds of all types of SMM, particularly cardiac and pulmonary SMM. These results highlight the broader risks of morbidity from cardiac disease and may guide targeted strategies to reduce SMM at the time of delivery and postpartum.