Miyoshi T, Maeno Y, Hamasaki T, et al. - In this multicenter, single-arm trial, researchers assessed protocol-defined transplacental treatment with regard to safety and effectiveness for fetal supraventricular tachycardia (SVT) and atrial flutter (AFL). For singleton pregnancies from 22 to < 37 weeks of gestation with sustained fetal SVT or AFL ≥ 180 beats/minute, they performed protocol-defined transplacental treatment using digoxin, sotalol, and flecainide. This investigation involved 50 patients enrolled at 15 institutions in Japan from 2010 to 2017; 17 patients had short ventriculoatrial (VA) SVT, 4 had long VA SVT, and 29 had AFL. Findings revealed the effectiveness as well as the tolerability of protocol-defined transplacental treatment for fetal SVT and AFL in 90% of patients. However, clinicians should be mindful of the possibility of serious adverse events in fetuses and of the possible recurrence of tachyarrhythmias within the first 2 weeks following birth.