Maternal Outcomes in Overseas Military Treatment Facilities: The Impact of Delivery Volume and Provider Experience from 2016-2024

INTRODUCTION: This study assessed whether delivery volume or other modifiable non-patient factors impact severe maternal morbidity (SMM) or 30-day readmission rates in military treatment facilities outside the continental U.S. (OCONUS MTFs), where personnel/non-personnel resources significantly differ from CONUS facilities. MATERIALS AND METHODS: Data from 25,263 deliveries over 9 years at 11 OCONUS MTFs were extracted from the Military Health System Data Repository. SMM diagnoses and 30-day readmissions were flagged. MTFs were grouped into 4 size quartiles by delivery volume. Obstetric provider availability and experience level were determined. Logistic regression calculated odds ratios for readmission and SMM by MTF size quartile and provider experience, with 90% confidence intervals. RESULTS: Of 25,263 deliveries, 141 (0.6%) SMM and 509 (2.0%) readmissions occurred. SMM regression found no significant associations with obstetric volume, provider experience, or subspecialty availability. For readmissions, MTFs in the upper volume quartile staffed exclusively by junior providers demonstrated significantly higher odds of readmission compared to those with mixed staffing (OR = 1.58, 90% CI = 1.11-2.23) or senior-only staffing (OR = 6.97, 90% CI = 2.55-19.01). Additionally, MTFs in the lower middle volume quartile with only junior providers showed higher readmission odds compared to MTFs in the upper middle quartile with mixed staffing (OR = 2.69, 90% CI = 1.01-7.19), and a trend toward increased readmission compared to MTFs in the lower middle quartile (OR = 2.04, 90% CI = 0.76-5.50). No consistent independent relationship between readmissions and obstetric volume was identified. CONCLUSIONS: Our findings suggest that non-patient factors, particularly MTF delivery volume and the experience level of available obstetric providers, are not associated with SMM but are significantly associated with 30-day maternal readmission rates in OCONUS MTFs. These modifiable factors should be considered in resource allocation and personnel assignments to optimize patient safety and quality of care in these unique settings.