Pregnancy increases the work demands on the heart by increasing blood volume and thereby cardiac output. Therefore, in pregnant patients with organic heart disease, arrhythmias may have significant hemodynamic consequences to the mother with harm to the fetus. As a result of improved medical therapy, an increasing number of women with cardiac diseases or rhythm disorders reach their reproductive years and require medication. Information on the effect of antiarrhythmic agents on the human fetus as well as the possible changes in therapeutic response during the altered state of pregnancy is limited. In principle, the approach to the treatment of arrhythmias in pregnant patients is similar to that in nonpregnant patients. Special consideration, however, must be given with regard to drug selection and dosage in order to avoid adverse effects on the mother and fetus.