We report the successful use of metoprolol in two fetuses with supraventricular tachycardia (SVT) that were refractory to flecainide monotherapy. The first fetus was diagnosed at 20 weeks' gestation with persistent SVT and hydrops (heart rate of 250–280 bpm, 1: 1 atrioventricular conduction, short ventriculoatrial time interval). Oral flecainide (100 mg four times/day) led to resolution of hydrops, but treatment was complicated by high flecainide levels (> 820 µg/L) and PR-interval and QT-interval prolongation (200 ms and 460 ms, respectively). Lowering the flecainide dose led to recurrence of SVT and hydrops. Following multispecialist and patient discussions, oral metoprolol (50 mg three times/day) was added at 31+ 0 weeks' gestation. Within 2 days, the fetal heart rate was 202 bpm and hydrops resolved. Within 6 days, normal sinus rhythm (heart rate, 119 bpm) was restored (Figure 1). Maternal systolic blood pressure (BP) remained> 90 mmHg and no side effects were experienced. A healthy infant (birth weight, 2.9 kg) was delivered in sinus rhythm at 38+ 2 weeks' gestation. A brief period of atrioventricular re-entry tachycardia (AVRT) occurred after birth and there was intermittent pre-excitation (Wolff–Parkinson–White pattern). Cord-blood concentration of metoprolol was 0.16 mg/L (therapeutic range, 0.02–0.34 mg/L), confirming placental transfer.