Date of Award

Spring 2026

Language

English

Embargo Period

4-30-2026

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

College/School/Department

Department of Epidemiology and Biostatistics

Program

Epidemiology

First Advisor

Dr. Alisson Appleton

Committee Members

Dr. Akiko Hosler, Dr. Danielle Wales

Keywords

omphalocele and gastroschisis, access to appropriate care, in-hospital mortality, hospitalization costs, HCUP KID

Subject Categories

Epidemiology

Abstract

Congenital abdominal wall defects (AWDs), including omphalocele (OM) and gastroschisis (GS), are rare but clinically significant conditions that require immediate surgical intervention and prolonged neonatal intensive care. OM is a midline defect in which abdominal organs protrude into the umbilical cord covered by a membranous sac, while GS is a full-thickness defect typically located to the right of the umbilicus through which organs protrude without protective coverage. OM is frequently associated with major co-occurring congenital anomalies and chromosomal abnormalities, while GS more commonly occurs as an isolated defect but requires more intensive surgical management. As survival rates have improved, research attention has shifted toward healthcare utilization, access to specialized care, and the economic burden of managing these conditions. However, important gaps remain in understanding the factors associated with delivery at appropriately equipped hospitals, the role of hospital procedure volume in mortality, and the determinants of hospitalization costs for these infants.

This dissertation examined three interrelated dimensions of inpatient care for infants with OM and GS in the United States: (1) geographic and socioeconomic factors associated with delivery at a high procedure volume hospital (HPVH), (2) the associations of delivery at HPVH and co-occurring congenital anomalies with in-hospital mortality, and (3) the associations of co-occurring congenital anomalies and household income with total hospitalization costs. All three studies used a retrospective cross-sectional design, pooling data from the 2016 and 2019 Healthcare Cost and Utilization Project (HCUP) Kids' Inpatient Database (KID), a nationally representative sample of pediatric inpatient discharges. The analytic sample included 1,850 OM (unweighted N = 1,394) and 2,834 GS (unweighted N = 2,174) infant hospitalizations identified using ICD-10-CM diagnosis codes. HPVHs were defined as those above the 75th percentile of the condition-specific weighted annual procedure volume distribution. Analyses were conducted separately for each condition using multilevel mixed-effects models with random hospital intercepts. Reduced models were developed using backward elimination with a 10% change-in-estimate criterion. Effect modification was tested in all three studies. Sensitivity analyses were conducted using survey-weighted approaches.

Paper 1 examined geographic and socioeconomic factors associated with delivery at HPVH. Patient residential location was not significantly associated with the outcome for either condition, suggesting that geographic barriers may not be the primary determinant of access to specialized care for infants with AWDs. For OM, co-occurring congenital anomalies were the strongest predictor of high procedure volume hospital delivery (aOR = 5.42, 95% CI: 3.53–8.30), followed by hospital teaching status and insurance type. Household income was not significantly associated with the outcome, and no evidence of effect modification by residential location was observed. For GS, high-income households had significantly lower odds of delivery at HPVH compared to medium-income households (aOR = 0.78, 95% CI: 0.65–0.94), and this association was particularly pronounced among urban residents (aOR = 0.64, 95% CI: 0.50–0.80). This finding suggested that factors beyond income and geography, including maternal education, provider relationships, and social barriers, may influence delivery location.

Paper 2 examined the associations of delivery at HPVH and co-occurring congenital anomalies with in-hospital mortality. Mortality rates differed substantially between conditions: 13.5% for OM and 3.1% for GS. Co-occurring congenital anomalies were strongly associated with mortality in both conditions (OM aOR = 6.88, 95% CI: 3.02–15.68; GS aOR = 3.60, 95% CI: 2.02–6.42), representing the strongest predictor identified in the analyses. Delivery at HPVH was not independently associated with mortality in either condition after adjustment, though the direction of association was consistently protective. Although the interaction between co-occurring anomalies and delivery at HPVH was not statistically significant, the pattern of conditional effects was clinically noteworthy: co-occurring anomalies were significantly associated with mortality only among infants not delivered at HPVH, suggesting that these hospitals may mitigate the mortality risk associated with co-occurring anomalies. Additional significant predictors included Hispanic race/ethnicity in OM, and rural residence and low birth weight in GS.

Paper 3 examined co-occurring congenital anomalies and household income as correlates of total hospitalization costs. Hospital charges were converted to costs using cost-to-charge ratios and adjusted to 2019 U.S. dollars. Median hospitalization costs were $3,215 for OM and $58,671 for GS, reflecting the more intensive surgical management typically required for GS. Co-occurring anomalies were significantly associated with higher costs in both conditions, with a larger relative association in OM (aCR = 1.32, 95% CI: 1.08–1.61) than in GS (aCR = 1.12, 95% CI: 1.05–1.19). Household income was not independently associated with costs after adjustment in either condition, and no evidence of effect modification by income was found. Hospital-level factors, particularly teaching status (OM aCR = 2.31; GS aCR = 3.49) and high procedure volume (OM aCR = 1.93; GS aCR = 2.40), were among the strongest correlates of costs in both conditions.

Across all three papers, co-occurring congenital anomalies emerged as a central factor shaping the trajectory of care for infants with AWDs, influencing delivery location, survival, and hospitalization costs. The distinct clinical profiles of OM and GS produced different patterns of association across outcomes, underscoring the importance of examining these conditions separately. Household income was not independently associated with mortality or hospitalization costs, though its role in access to HPVHs was less straightforward, particularly for GS. Hospital-level characteristics, including teaching status and procedure volume, were consistently among the strongest correlates across all three outcomes. These findings support the importance of comprehensive prenatal screening and early identification of co-occurring anomalies, regionalization of care that directs high-risk deliveries to experienced centers, and multifaceted approaches to addressing disparities in access to specialized care. Future research using linked prenatal care and hospital discharge data, longitudinal cost studies, and qualitative investigations of family experiences would provide a more complete understanding of the care and outcomes of infants with AWDs.

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