BACKGROUND: The obstetric comorbidity index (OB-CMI) summarizes the burden of maternal comorbidities into a single number and holds promise as a maternal risk-assessment tool.
OBJECTIVE: The aim of this study is to assess the clinical performance of this comorbidity-based screening tool to accurately identify women on labor and delivery at risk of severe maternal morbidity (SMM) on labor and delivery (L&D) in real time.
STUDY DESIGN: All patients with pregnancies at or beyond 23 weeks' gestation presenting to L&D at a single tertiary-care center from February through July 2018 were included in the study. The patient's primary L&D nurse assessed patient comorbidities and calculated the patient's OB-CMI. The score was recalculated at each 12-hour shift change. A multidisciplinary panel of clinicians determined whether patients experienced SMM based on the American College of Obstetrics and Gynecology and Society for Maternal-Fetal Medicine consensus definition, blinded to the patient's OB-CMI score. We analyzed the association between the OB-CMI score and the occurrence of SMM.
RESULTS: The study included 2,828 women, of whom 1.73% developed SMM (n=49). The OB-CMI ranged from 0 to 15 for women in the study cohort with a median OB-CMI of 1 (interquartile range (IQR) 0-3). The median OB-CMI score for women experiencing the SMM was 5 (IQR, 3-7) compared to a median of 1 (IQR, 0-3) for those without SMM (p<0.01). The frequency of SMM increased from 0.41% for those with a score of 0 to 18.75% for those with a score greater than or equal to 9. For every one-point increase in the score patients experienced a 1.55 increase in odds of SMM (95% confidence interval (CI), 1.42-1.70). The c-statistic for the OB-CMI score was 0.83 (95% CI 0.76-0.89) indicating strong discrimination.
CONCLUSIONS: The OB-CMI can prospectively identify women at risk of severe maternal morbidity in a clinical setting. A particular strength of the OB-CMI is its ability to integrate multiple compounding comorbidities and highlight the cumulative risk associated with the patients' conditions. Routine clinical use of the OB-CMI has the potential to identify at-risk women warranting increased surveillance and targeted care to prevent adverse maternal outcomes.