BackgroundCardiac dysfunction is a key determinant of outcome in congenital diaphragmatic hernia (CDH). Pro-b-type natriuretic peptide (proBNP) is used as a prognosticator in heart failure and cardiomyopathy. We hypothesized that proBNP levels would be associated with ventricular dysfunction and high-risk disease in CDH. MethodsPatients in the CDH Study Group (CDHSG) from 2015–2019 with at least one proBNP value were included. Ventricular function was determined using echocardiograms from the first 48 h of life. ResultsA total of 2,337 patients were identified, and 212 (9%) had at least one proBNP value. Of those, 3 (1.5%) patients had CDHSG stage A defects, 58 (29.6%) B, 111 (56.6%) C, and 24 (12.2%) D. Patients with high-risk defects (Stage C/D) had higher proBNP compared with low-risk defects (Stage A/B) (14,281 vs. 5,025, p = 0.007). ProBNP was significantly elevated in patients who died (median 14,100, IQR 4,377–22,900 vs 4,911, IQR 1,883–9,810) (p<0.001). Ventricular dysfunction was associated with higher proBNP than normal ventricular function (8,379 vs. 4,778, p = 0.005). No proBNP value was both sensitive and specific for ventricular dysfunction (AUC=0.61). ConclusionAmong CDH patients, elevated proBNP was associated with high-risk defects, ventricular dysfunction, and mortality. ProBNP shows promise as a biomarker in CDH-associated cardiac dysfunction.