Resolution of tachyarrhythmia-related fetal hydrops after corticosteroid administration for fetal lung maturation

A case of hydrops fetalis (HF) that resolved after corticosteroid therapy despite persisting fetal tachycardia of 190 bpm is reported. The fetus with confirmed normal karyotype had HF in the presence of atrial flutter and sustained ventricular rate of 200-210 bpm at gestational week (GW) 31(-6/7). Aetiologies of HF other than fetal tachyarrhythmia were unlikely in this infant. The patient's family declined pharmacological treatment with maternal digoxin and desired to continue pregnancy with only intensive monitoring of fetal condition. Maternal transplacental β-methasone was given to facilitate fetal lung maturation. The fetal tachyarrhythmia ameliorated to 190 bpm at GW 32(-5/7) and HF gradually disappeared by birth. The otherwise healthy female neonate weighing 3050 g born at GW 37(-0/7) was successfully treated with cardioversion performed 60 min after birth. This case suggested that corticosteroid therapy contributed to the resolution of HF associated with tachyarrhythmia.