Up to 40% of newborn infants of women with type 1 diabetes have echocardiographic signs of cardiomyopathy. Increased plasma concentrations of B-type natriuretic peptide (BNP) and its precursor (proBNP) are markers of cardiac failure and hypoxia in adults. In this study, we investigated whether plasma concentrations of proBNP and/or BNP are increased in infants of women with type 1 diabetes.