Objective: Congenital complete heart block is associated with maternal autoantibodies to Ro and La proteins, which injure the fetal cardiac conduction system. We administered dexamethasone to the mothers of five fetuses with heart block caused by maternal antibodies.
Study design: We diagnosed five cases of fetal heart block at 20 to 23 weeks and treated all mothers with dexamethasone 4 mg orally each day for the remainder of the pregnancy. All patients were positive for anti-SS-A (anti-Ro) and/or anti-SS-B (anti-La) antibodies.
Results: Four patients had complete heart block, and one had second-degree block. In two patients (one with complete heart block, one with second-degree heart block) the degree of block lessened with treatment. Hydrops in three complete heart block patients resolved after treatment. Maternal antibody levels did not change. Matched maternal and cord samples at delivery showed similar antibody levels.
Conclusions: Complete heart block can respond to transplacental glucocorticoid therapy with improved cardiac conduction. Because there may be a concurrent myocarditis, treatment in utero may also improve cardiac contractility, leading to the observed rapid resolution of hydrops. Treatment with steroids that cross the placenta should be considered for newly diagnosed cases of complete heart block with positive antibody screens.