External Validation of the Clinical Obstetric Comorbidity Index across a Diverse Health System

Abstract

Objective

The clinically-modified obstetric comorbidity index (OB-CMI) is a comorbidity-based scoring system that has been validated to predict severe maternal morbidity (SMM) in a single tertiary, academic hospital using an internal SMM definition. We aimed to validate the OB-CMI for the prediction of SMM as defined by the CDC during delivery admissions across a diverse health system.

Study Design

This is a retrospective cohort study evaluating all deliveries in a large health system encompassing academic and community hospitals. Data from 2019 to 2021 were extracted from the electronic health record (EHR) and validated with chart review. An OB-CMI score was calculated for each patient using established diagnosis codes and EHR data. The primary outcome was nontransfusion SMM (defined by the CDC) during the delivery admission. Patient characteristics were evaluated by the hospital, and hospital-specific receiver-operator characteristic (ROC) curves were constructed and compared.

Results

In total, 42,130 deliveries were included with significant differences in all demographic, clinical, and obstetric characteristics across the hospitals including age, BMI, race/ethnicity, insurance type, preterm birth, and preeclampsia rates. Median OB-CMI score and rate of elevated OB-CMI score (≥6) were also significantly different. ROC curves for OB-CMI and SMM for each hospital are noted in the figure with an area under the curve range from 0.77 to 0.83, and no significant differences across hospitals (p = 0.32).

Conclusion

In a large cohort of patients delivering across a diverse hospital system, the clinical OB-CMI score similarly predicted SMM despite differences in demographic and clinical characteristics among the hospitals. This validation of the OB-CMI supports the use of this scoring system in variegated clinical settings, which can inform widescale uptake and clinical integration of OB-CMI scoring to improve obstetric risk stratification.

Key Points

• The clinically-modified OB-CMI consistently predicted nontransfusion SMM across multiple hospitals.

• This OB-CMI can be used for obstetric risk stratification across different clinical settings.

• Future research should explore the impact of using the OB-CMI to mitigate risk in clinical practice.

Keywords

severe maternal morbidity - obstetric comorbidity index - risk prediction - validation

Publikationsverlauf

Eingereicht: 12. März 2025

Angenommen: 02. April 2025

Accepted Manuscript online:
02. April 2025

Artikel online veröffentlicht:
06. Mai 2025

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