A seventeen-year-old primigravida, without structural heart disease or
abnormalities of serum chemistry, presented with complaints of palpit
ations during the twenty-fourth week of gestation. Holter monitoring r
evealed long episodes of accelerated idioventricular rhythm. The autho
rs are not aware of similar reports, but this entity may be more commo
n than realized because of the relative infrequency of rhythm monitori
ng in this particular group.