Background: The aim of our study was to characterize echocardiographic changes during pregnancy in women with known LVOT obstruction or AS compared to the healthy pregnancy controls, and to assess the relationship with pregnancy outcomes. Methods: We retrospectively studied 34 pregnant patients with congenital LVOT obstruction or AS with healthy age-matched pregnant controls. Patients with other significant valvular lesions, structural heart disease (LVEF <40%), or prior valve surgery were excluded. All LVOTO/AS patients underwent a minimum of 2 consecutive echocardiograms between 1 year pre-conception up to 1 year postpartum, with at least 2 studies during the pregnancy. Comprehensive echocardiographic evaluation was performed including speckle-tracking LV global longitudinal strain. Results: A total of 83 echocardiograms from the study group and 34 echocardiograms from the control group were evaluated. Over the range of LVOTO/AS, a significantly greater increase in the AV gradients and LV and LA volumes were observed as compared with the controls. In the sub-group of LVOTO/AS pregnant women with > moderate (n=8) vs.