Pathological heartHeart rhythm disturbances in the fetusFetus are uncommon, however, being able to correctly diagnose the type of arrhythmiaArrhythmia and instigate the appropriate treatment is crucial for a good fetalFetal outcome. In contrast to postnatal life, the diagnosisDiagnosis is usually made using ultrasound rather than electrocardiographic techniques. TachycardiasTachycardia, bradycardiasBradycardia and irregular fetal heartFetal heart rhythms are discussed including the approach to diagnosisDiagnosis and management.