Clapp MA, et al. - In view of the observation that the levels of maternal care reflect a hospital’s ability to manage patients with certain conditions associated with increased risk of complications, researchers performed a comparison of outcomes among high- and low-risk patients between high and low acuity hospitals. As per their hypothesis, hospitals caring for a high rate of high-risk patients, which they considered “high acuity” centers, would have a lower risk of severe maternal morbidity among high-risk patients compared to low acuity centers. Outcomes suggest a higher risk of severe maternal morbidity among high-risk patients at low acuity hospitals compared to high acuity centers. Findings thereby affirm the concept of regionalization of maternity care to improve outcomes for high-risk patients.

Methods

• Researchers searched the 2013 Nationwide Readmission Database to identify deliveries.
• They assigned a patient’s comorbidity index based on diagnosis and procedures codes using previously validated methods; a comorbidity index ≥3 has been associated with increased odds of severe maternal morbidity.
• Classification of patients as either low, intermediate, or high risk by their comorbidity index was performed for analysis.
• They excluded patients at hospitals with <100 deliveries per year and transferred patients.
• They defined a hospital as low or high acuity if it was in the bottom or top quartile, respectively, based on its percent of patients with comorbidity index ≥3.
• They constructed log-binomial regression models to assess the effects of a patient’s comorbidity index group on the risk of severe morbidity in high and low acuity hospitals.
• For available patient and hospital factors, the models were controlled.
• For the regression, they used patient-level data with robust standard errors clustered at the level of the hospital.
• They used the Wald test to assess for the effect modification between comorbidity index group and hospital acuity.

Results

• The inclusion criteria was met by 1,656,659 delivering patients from 1,203 hospitals.
• The overall sample had 58.7% low-risk, 39.0% intermediate-risk, and 2.3% high-risk patients, and the overall rate of severe maternal morbidity was 1.2%.
• In low acuity hospitals, less than 3.7% of delivering patients had a high-risk condition.
• In comparison, more than 7.1% patients had a high-risk condition in high acuity centers.
• Slightly increased risk of morbidity was noted in intermediate-risk patients in both low acuity and high acuity centers compared to low-risk patients [adjusted risk ratios 1.53 (95% confidence interval 1.33-1.77) vs 1.57 (95% confidence interval 1.49-1.65)] in the adjusted analysis.
• However, the high-risk population showed a notable difference in the adjusted risk ratios for severe maternal morbidity: the adjusted risk ratio was 9.55 (95% confidence interval 6.83-13.35) in low acuity hospitals compared to 6.50 (95% confidence interval 5.94-7.09) in high acuity hospitals.