Infants born preterm often have impaired pulmonary function, but little is known regarding long-term implications on right-heart function as these patients reach adulthood. We performed 4D flow MRI during rest and exercise in young adults born preterm and age-matched controls to compare their right heart function and efficiency. While flow and velocity in the pulmonary artery appeared similar in both groups, preterm subjects demonstrated increased kinetic energy in the right ventricle (RV) per unit of ejected blood. Pathline visualizations in the right ventricle suggested less structured filling during diastole. These data suggests decreased RV efficiency in preterm adults.