The Obstetric Comorbidity Index (OB-CMI) and its association with ICU admission and length of hospital stay in pregnant patients with pulmonary hypertension: a retrospective cohort study (1996-2025).

BACKGROUND

Pulmonary hypertension in pregnancy is associated with adverse pregnancy outcomes, such as prolonged hospitalization, intensive care unit (ICU) admission, and high maternal mortality. The Obstetric Comorbidity Index (OB-CMI) assesses maternal risk for these outcomes; however, its predictive power in patients with pulmonary hypertension remains unknown. This study evaluates maternal and neonatal outcomes in patients with pulmonary hypertension and examines whether a higher comorbidity burden is associated with longer hospitalization and ICU admission.

METHODS

A retrospective cohort study was conducted using electronic health records from Mass General Brigham and Tufts Medical Center (1996-July 2025). Patients with pulmonary hypertension and pregnancies beyond 20 weeks' gestation were identified using the International Classification of Disease-9/10 codes. Data were collected via manual chart review, and descriptive statistics and univariate regression analyses were performed (P < 0.05).

RESULTS

Sixty-five pregnancies among 61 patients were identified. The median maternal age was 32.9 (interquartile range 28.9-36.6) years. The maternal mortality rate was 3 %, with both deaths occurring before 2000. Most patients (56.9 %) had cesarean delivery under epidural anesthesia (69.2 %). Median OB-CMI was 9, and median hospitalization was 6 days. Pulmonary artery pressure was associated with prolonged hospitalization (P = 0.004) and ICU admission (P = 0.027). OB-CMI showed borderline association with ICU admission (P = 0.046), but not hospitalization duration (P = 0.580).

CONCLUSIONS

In patients with pulmonary hypertension, ICU admission and prolonged hospitalization were common and associated with pulmonary arterial pressure but not OB-CMI. Further studies are needed to develop scoring tools specific to pulmonary hypertension patients to improve risk assessment.