A minute ventilation sensing rate responsive pacemaker was implanted in a 29-week pregnant woman with symptomatic complete atrioventricular (AV) block under echocardiographic and electrocardiographic (ECG) guidance. Satisfactory rate responses during a submaximal treadmill exercise test and daily activities were achieved. The course of pregnancy and cesarean section is discussed. During the cesarean section and after the delivery of the baby, changes in the ventilator settings confirmed that the pacing rate was closely correlated with both the tidal volume (r = 0.94, P less than 0.01) and the respiratory rate (r = 0.93, P less than 0.05).