Persistent bradycardia is an uncommon cardiac problem in fetuses but carries a high mortality in those with a ventricular rate <55 bpm. Fetal heart block is one of the most common causes of persistent fetal bradycardia (PFB). An optimal method for assessing and monitoring cardiovascular compensation in the setting of PFB due to heart block has not been fully established. We report the application of two-dimensional and Doppler echocardiography in close monitoring of cardiac function and hemodynamics in a third-trimester fetus with a ventricular rate <55 bpm due to heart block, which assisted in successful management of the pregnancy to term. Hemodynamic and cardiac adaptive changes in compromised fetuses, particularly due to heart block, are discussed.