Post-Transformation Update: Volume as an Indicator for Outcomes for Severe Maternal Morbidity in the Military Health System

Background: Hospital delivery volume has been linked to severe maternal morbidity (SMM), which increases medical costs, readmissions, hospital stays, and mortality risk. During Fiscal Years (FY) 2019–2023, the Military Health System (MHS) rolled out a new electronic health record, merged facilities under Defense Health Agency (DHA) management, and weathered the COVID-19 pandemic. This study aimed to examine the association between delivery volume and odds of SMM and 30-day readmissions for deliveries at U.S. military hospitals for FY 2019–2023. Methods: This cross-sectional study analyzed healthcare claims data from MHS beneficiary women aged 15–54 years delivering FY 2019–2023. Delivery volume was measured using International Classification of Diseases-10 (ICD-10) and Medicare Severity-Diagnosis Related Group codes. Military hospitals were grouped into quartiles by volume over the study period. SMM was measured by 21 ICD-10 indicators (any/none). Any postpartum readmission (yes/no) to the same hospital within 30 days of discharge was included. Covariables included hospital identifier and maternal comorbidities and demographics associated with each delivery. Stepwise logistic regression was performed. Results: Women delivering at hospitals in the lowest, lower-middle, and highest volume quartiles had significantly lower (19–30%) odds of SMM compared with the upper–middle quartile ( p < 0.05). Those delivering at lower and lower-middle quartile hospitals had significantly higher (29–46%) odds of 30-day readmissions compared with the upper–middle quartile ( p < 0.05), with no significant difference found among those in the highest quartile. Conclusions: Delivery volume was significantly associated with SMM and 30-day readmission odds among MHS deliveries FY 2019–2023. This differs from previous FY 2015–2018 findings, therefore concurrent effects of the DHA transition and COVID-19 pandemic cannot be ruled out.