55: The association between hospital acuity and severe maternal morbidity in a nationwide sample

Abstract

In the context of the recently established levels of maternal care, we sought to compare the impact of pre-existing comorbidities on a woman’s risk for severe maternal morbidity in low and high acuity hospitals. Deliveries were identified in the 2013 Nationwide Readmission Database. A patient’s comorbidity index (CI) was assigned using ICD-9 codes according to previously validated methods; a CI ≥3 has been associated with increased odds of severe maternal morbidity. Patients were grouped by their CI for analysis. Patients at hospitals with <100 deliveries per year and transferred patients were excluded. A hospital was defined as low or high acuity if it was in the bottom or top quartile, respectively, based on its rate of women delivering with CI ≥3. Logistic regression models were constructed to assess the effects of a patient’s CI group on the odds of severe morbidity in high and low acuity hospitals. The models controlled for available patient and hospital factors. The regression used patient-level data with robust standard errors clustered at the level of the hospital to account for intraclass correlation. The Wald test was used to assess for the effect modification between CI group and hospital acuity. 409,053 patients in 301 low acuity centers, and 406,311 patients in 301 high acuity centers met criteria for inclusion. In low acuity hospitals, the median rate of patients with CI≥3 was 2.8% (interquartile range (IQR) 2.2-3.3%) and the median delivery volume was 425 (IQR 229-792). In high acuity hospitals, the median rate of patients with CI≥3 was 8.8% (IQR 7.7-11.1%) and the median delivery volume was 1,991 (IQR 1,061-3,148). There was a significant effect between CI group and hospital acuity on the odds of severe morbidity (p=0.004). Figure 1 shows that the odds of severe morbidity increase with increasing CI groups for both high and low acuity hospitals. However, while patients with low CIs had similar odds of severe morbidity at low and high acuity hospitals, women with high CIs had much lower odds of severe morbidity at high acuity hospitals. Patients with multiple comorbidities have lower rates of severe maternal morbidity at high acuity hospitals. These findings support the concept of maternity care regionalization to improve outcomes for high-risk patients.