Because of quantitative echocardiographic limitations of fetal ventricular volumes as well as poor windows, we sought to determine if real-time magnetic resonance imaging (MRI) could be used. Real-time, functional, true fast imaging with steady-state precession, cardiac MRI was performed on 2 fetuses (one with hypoplastic left heart syndrome and one with ductal constriction). Fetal echocardiography was performed and cardiac index by Doppler was used to validate volume measures by MRI. This technique was able to visualize the beating heart and assess ventricular volumes. Cardiac index and assessment of right ventricular hypertrophy and dilation by echocardiography were consistent with the ventricular volumes and right ventricular hypertrophy obtained by cardiac MRI. Real-time, functional fetal cardiac MRI is possible and can be used to quantitatively assess ventricular volumes and cardiac index in utero. Copyright (c) 2005 S. Karger AG, Basel.