The combination of fixed outflow obstruction from aortic stenosis (AS) and the hemodynamic changes of pregnancy increased the risk of maternal or fetal deterioration. Left ventricular (LV) response in patients with AS to the hemodynamic changes of pregnancy has not been examined. We studied and compared myocardial mechanics with echocardiography in 3 groups of 10 women each, including (1) pregnant with bicuspid aortic valve (BAV; peak aortic gradient 59 +/-7 mm Hg, aortic valve area 0.9 +/- 0.04 cm2), (2) pregnant without BAV, and (3) nonpregnant, healthy volunteer. Measurements in the pregnant BAV group were made on 3 occasions, within a year before pregnancy (baseline), in the antepartum period, and at least 6 weeks postpartum. Tissue tracking ultrasound was used to assess longitudinal strain and LV twist. During pregnancy, peak AS gradient rose from 59 +/- 7 to 70 +/- 9 mm Hg (p = 0.004) whereas valve area remained unchanged 0.9 +/- 0.04 to 0.8 +/- 0.04 cm2 (p = 0.48) as compared with baseline (before pregnancy). Overall, in all patients, there was no significant change in the longitudinal strain (-22 +/- 1, -21 +/- 0.6, -20 +/- 0.6 percent, p = 0.21)] at baseline, during pregnancy, or after pregnancy, respectively. Patients with AS had a higher baseline LV twist compared with both control groups (5.4 +/- 0.3, pregnant, with AS; 4.1 +/- 0.8, pregnant, without AS; 3.6 +/- 0.3, nonpregnant volunteer; expressed in degrees; p = 0.023). Additionally, all but 2 patients had a significant increase in LV twist during pregnancy compared with baseline. These 2 women had symptomatic deterioration requiring urgent aortic balloon valvuloplasty. Postpartum, in all AS patients, LV twist returned to antepartum values. In conclusion, we found that LV twist was significantly increased in women with congenital AS. During pregnancy, LV twist further increased in the antepartum period, except in those women who experienced functional deterioration.