(521) Association of obstetric comorbidity index with postpartum hemorrhage in a large health system

Postpartum hemorrhage (PPH) is the leading cause of severe maternal morbidity in the United States and of maternal mortality worldwide, but existing risk-prediction tools have low sensitivity and specificity. We sought to examine whether the Obstetric Comorbidity Index (OB-CMI), which has been validated to predict severe maternal morbidity, was associated with PPH in a large health system.

Study Design:

This retrospective cohort study included all patients admitted for delivery at ≥24 weeks gestational age between 3/2021 and 11/2022 at 8 hospitals in an integrated healthcare system with an OB-CMI score recorded on admission. Patients were categorized into low- (OB-CMI ≤2), medium- (OB-CMI 3-5), and high-risk (OB-CMI ≥6) categories. Logistic regressions were used to assess the odds of PPH (estimated blood loss, EBL ≥1000 mL) by OB-CMI category with standard errors clustered at the level of the hospital. The odds of PPH by OB-CMI category were also compared among the following subgroups to evaluate if the associations varied: hospital, self-reported race, self-reported ethnicity, parity.

Results:

24,877 patients were included: 18,639 (74.9%) were low-risk, 4,831 (19.4%) were medium-risk, and 1,407 (5.7%) were high-risk. The rates of PPH were 8.9%, 12.6%, and 20.3% in the low-, medium-, and high-risk groups. The odds ratio of PPH for medium- and high-risk groups were 1.47 (95% CI 1.31-1.65) and 2.60 (95% CI 2.10-3.22). Similar magnitudes of effect were seen when the logistic models were stratified by hospital, race, ethnicity, and parity (Figure 1), though sample size limited the ability to fully evaluate all hospital and race subgroups.
 

Conclusion:

In a large healthcare system, OB-CMI was reliably associated with PPH. Future work should compare this tool to other hemorrhage risk stratification tools to determine how these tools can be accurately and effectively used to prevent PPH and associated morbidity.