ABSTRACT
Normal fetal heart rate is between 110 and 160 bpm. Periods of transient bradycardia or tachycardia are common and are of no clinical significance. When a fetal cardiac arrhythmia is diagnosed, extracardiac causes of tachycardia such as maternal medication, maternal pyrexia, and hyperthyroidism must first be excluded. Once extracardiac causes of fetal arrhythmia have been excluded, the fetal heart should be carefully examined to exclude structural abnormalities. Fetal arrhythmias can be part of complex structural heart conditions and in these cases, prognosis will be mostly determined by the underlying condition. Fetal arrhythmias can also present with some degree of heart failure, and it is important to document the presence or absence of cardiomegaly, atrioventricular valve regurgitation, pericardial effusion, and hydrops. Ectopic beats are the most common form of fetal arrhythmia and usually present in the third trimester. Ectopic beats are caused by an extra beat arising prematurely and outside the natural pacemaker.
