Effects of pregnancy on the electrocardiogram in healthy subjects during strenuous exercise, ,

OBJECTIVE: Our purpose was to examine the nature and the frequency of electrocardiographic changes at rest and after bicycle exercise in early and late gestation compared with a group of nonpregnant subjects. STUDY DESIGN: Thirty-nine pregnant subjects had electrically braked bicycle exercise early and late in gestation. Eight nonpregnant subjects served as controls. Twelve-lead electrocardiograms were obtained during rest, exercise, and recovery. All electrocardiograms were analyzed by a cardiologist blinded to subject group and stage of the pregnancy. Data were analyzed by analysis of variance for repeated measures, and contingency tables were used to compare findings at rest and during exercise between the time periods. A p value <0.05 was considered significant. RESULTS: T-wave inversion in V2 was more frequent in the pregnant than the nonpregnant subjects (p< 0.01). Subjects “late” in pregnancy had significantly fewer Q waves in II, III, and aVF than the nonpregnant group did. With exercise the time to onset of maximum ST depression was significantly shorter during pregnancy. CONCLUSION: Although minor electrocardiographic changes were found at rest and during exercise between the two groups, these should be considered normal unless associated with significant symptoms. (Am J Obstet Gynecol 1996;175:1360-4.)