Over 25% of pregnant women fall. Increased gait variability, particularly in regard to step width and trunk frontal plane movement, has been observed in some populations at high risk of falling. Pregnant women have been shown to have greater mediolateral translation of the trunk during walking. However, it is not known if pregnant women, particularly those who have fallen while pregnant, have increased variability during gait. PURPOSE: To examine the effects of pregnancy and fall history on within-subject step width and trunk variability during gait. METHODS: Data were collected on 29 pregnant subjects and on 40 controls. Pregnant women self-reported to be "fallers"(n=15) or "non-fallers" (n=14). An 8-camera motion capture system (120 Hz) was used to collect five trials of subjects walking at their freely-chosen speed. Right foot heel strike (RHS) and left foot toe off were determined from force plate data (1080 Hz). The 3D angles of the thorax and pelvis were assessed at RHS. Frontal plane movement of the C7 marker and the ROMs of the thorax and pelvis during gait were calculated. Variability was defined as the within-subject standard deviation of each variable over the 5 trials. A two-factor ANOVA (trimester (control, 2nd, 3rd) x fall group (control, pregnant faller, pregnant non-faller)) was performed on each measure (á=0.05). RESULTS: No differences in the variability of step width or frontal plane motion were found between pregnant women and controls or between pregnant fallers and non-fallers (p>0.05). Variability of the thoracic rotational ROM was less in the 3rd trimester than controls (1.1 +/- 0.5 vs 1.6 +/- 0.7, p=0.03), as well as in the pregnant non-fallers compared to controls (1.1 +/- 0.7 vs 1.6 +/- 0.7, p=0.02). CONCLUSIONS: Other populations who fall (e.g. the elderly) demonstrate heightened variability in specific gait measures; however, pregnant women do not exhibit this, despite the fact that they are at a high risk of falling. This may indicate that pregnant women do not fall for the same reasons that others fall. The decreased variability in thoracic rotational ROM seen in the pregnant women in the 3rd trimester and the pregnant non-fallers may reflect pregnancy-related adaptations to movement in order to protect against a fall.