Reversal of Fetal Heart Block in Antibody-Positive Mother After Hydroxychloroquine and Dexamethasone.

Maternal autoantibody-related complete heart block in the fetus is considered irreversible. During prenatal care for a 25-year-old nulliparous Hispanic woman with newly diagnosed nephrotic-range proteinuria and positive anti-nuclear antigen antibody, complete fetal heart block with a ventricular rate of 60 beats per minute was detected on a fetal echocardiogram at 28-week gestation. A small pericardial effusion and ascites were noted consistent with fetal hydrops. Dexamethasone and hydroxychloroquine were initiated. Fetal rhythm improved to Mobitz type 1 second-degree heart block, with a ventricular rate of 91 beats per minute. The fetus was born prematurely at 34-week gestation with second-degree heart block which improved to first-degree heart block prior to hospital discharge. First-degree heart block persisted at 2 years of age with a P-R interval of 185 ms. Transplacental treatment with dexamethasone and hydroxychloroquine was associated with sustained reversal of complete heart block to sinus rhythm.