The use of continuous fetal heart rate (FHR) recordings to monitor fetal well-being during labor is standard clinical practice in developed countries. Little is known about the relationship, if any, that exists between these FHR abnormalities and the fetal cardiac musculature and function. The aim of this study was to investigate umbilical artery serum levels of cardiac troponin I, a sensitive and specific marker of myocardial necrosis, and N-terminal pro-brain natriuretic peptide (pro-BNP), a sensitive marker of left ventricular dysfunction, in relation to FHR abnormalities. Umbilical artery blood samples were taken from 27 cases immediately after delivery of the infant. There was evidence of significant FHR abnormalities in I I of these cases (group 2) and the FHR recording was normal in 16 cases (group 1). The mean N-terminal pro-BNP level in umbilical artery serum in group 2 was 413 fmol/L (SEM = 85) and in group 1 was 223 fmol/L (SEM = 28)(p = 0.022). There was no significant difference observed in cardiac troponin I levels between the two groups. Umbilical artery serum N-terminal pro-BNP is elevated in association with fetal heart rate abnormality in the late stage of labor. This finding suggests that some degree of cardiac compromise accompanies FHR abnormality.