A comorbidity-based screening tool to predict severe maternal morbidity at the time of delivery

Abstract

The obstetric comorbidity index summarizes the burden of maternal comorbidities into a single number and holds promise as a maternal risk-assessment tool. The aim of this study was to assess the clinical performance of this comorbidity-based screening tool to accurately identify women on labor and delivery who are at risk of severe maternal morbidity on labor and delivery in real time. All patients with pregnancies ≥23 weeks gestation presenting to labor and delivery at a single tertiary-care center from February through July 2018 were included in the study. The patient's primary labor and delivery nurse assessed patient comorbidities and calculated the patient's obstetric comorbidity index. The score was recalculated at each 12-hour shift change. A multidisciplinary panel of clinicians determined whether patients experienced severe maternal morbidity based on the American College of Obstetrics and Gynecology and Society for Maternal-Fetal Medicine consensus definition, blinded to the patient's obstetric comorbidity index score. We analyzed the association between the obstetric comorbidity index score and the occurrence of severe maternal morbidity. The study included 2828 women, of whom 1.73% experience severe maternal morbidity (n=49). The obstetric comorbidity index ranged from 0-15 for women in the study cohort, with a median obstetric comorbidity index of 1 (interquartile range, 0-3). The median obstetric comorbidity index score for women who experienced the severe maternal morbidity was 5 (interquartile range, 3-7) compared with a median of 1 (interquartile range, 0-3) for those without severe maternal morbidity (P<.01). The frequency of severe maternal morbidity increased from 0.41% for those with a score of 0 to 18.75% for those with a score ≥9. For every 1-point increase in the score, patients experienced a 1.55 increase in odds of severe maternal morbidity (95% confidence interval, 1.42-1.70). The c-statistic for the obstetric comorbidity index score was 0.83 (95% confidence interval, 0.76-0.89), which indicated strong discrimination. The obstetric comorbidity index can prospectively identify women at risk of severe maternal morbidity in a clinical setting. A particular strength of the obstetric comorbidity index is its ability to integrate multiple compounding comorbidities and highlight the cumulative risk that is associated with the patients' conditions. Routine clinical use of the obstetric comorbidity index has the potential to identify at-risk women whose condition warrants increased surveillance and targeted care to prevent adverse maternal outcomes.