Little is known about the influence of hemodynamic changes on ventricular performance during pregnancy in patients with congenital heart disease. A prospective evaluation was made of 17 pregnancies in 11 women with repaired tetralogy of Fallot (ToF). Twenty age-matched non-pregnant women and 41 stable pregnant women without heart disease were studied as controls. Blood pressure (BP), heart rate (HR), left ventricular end-diastolic dimension (LVEDD) and ejection fraction (LVEF), and the Tei index were measured before pregnancy; during the 1st, 2nd, and 3rd trimesters; and after delivery. BP and HR gradually increased during the pregnancy in both groups. The LVEDD in the controls increased throughout the gestation period, then decreased after delivery. In contrast, the LVEDD in the ToF was significantly smaller than that of the controls, and no such increase was observed. The LVEF did not change throughout pregnancy or after the delivery in either group. Although the Tei index of the controls did not change throughout the pregnancy, in the ToF group it was significantly increased in the 2nd and 3rd trimester and then decreased after delivery. These findings suggest that subclinical left ventricular intolerance for volume overload, probably because of the smaller LVEDD, may exist during pregnancy in patients with a repaired ToF. (Circ J 2003; 67: 682 - 686)