Balance (perceived and actual) and preferred stance width during pregnancy

Background Pregnant women often remark that their balance degrades during pregnancy; however, it appears that no studies have documented the gravida’s perception of her balance nor measured direction-specific changes in balance throughout pregnancy or after delivery. Methods Thirty women, fifteen pregnant and fifteen non-pregnant controls, were tested monthly and through 6-month postpartum. For each session, perceived degradation in sense of balance, laboratory-based balance measures, stance width, and the number of falls since the previous session were recorded. Laboratory-based balance measures, quantified by direction-specific measures of postural sway, were computed from ten 30 s quiet-standing trials on a stationary force platform. Repeated-measures analysis of variance, paired t-tests, and Pearson correlations were use to examine group and time effects. Findings For the pregnant group, perceived balance degradation and stance width were highly correlated (r = 0.94). Both increased during pregnancy (Pless-than-or-equals, slant0.016) and dropped to near-control levels after delivery (Pless-than-or-equals, slant0.004). Compared to the control group, pregnant subjects displayed increased sway, especially in the anterior–posterior and radial directions (Pless-than-or-equals, slant0.039). Anterior–posterior sway measures strongly correlated with perceived balance (0.82 > r > 0.72) and also decreased significantly between the third trimester and postpartum (Pless-than-or-equals, slant0.029). Interestingly, medial–lateral balance measures varied little during pregnancy, but increased after delivery. Contrary to recent work suggesting fall rates of 25%, only 13% of our subjects (n = 2) fell during pregnancy. Interpretation Perceived degradation in balance during pregnancy was strongly related to increasing postural sway instability in the anterior–posterior direction. Lateral stability was maintained during pregnancy and likely accomplished by increasing stance width.