title: Balance (perceived and actual) and preferred stance width during pregnancy.
abstract: 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 30s 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.
  
  
  RESULTS
  For the pregnant group, perceived balance degradation and stance width were highly correlated (r = 0.94). Both increased during pregnancy (P < or = 0.016) and dropped to near-control levels after delivery (P < or = 0.004). Compared to the control group, pregnant subjects displayed increased sway, especially in the anterior-posterior and radial directions (P < or = 0.039). Anterior-posterior sway measures strongly correlated with perceived balance (0.82 > r > 0.72) and also decreased significantly between the third trimester and postpartum (P < or = 0.029). 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, 124 Mechanical Engineering Building, MC-244, 1206 West Green Street, Urbana, IL 61801, USA.
authors.forename: John
authors.initials: J
authors.lastname: Jang
authors.forename: Katherine T
authors.initials: KT
authors.lastname: Hsiao
authors.forename: Elizabeth T
authors.initials: ET
authors.lastname: Hsiao-Wecksler
mesh_terms: D000058:Accidental Falls / Q000706:statistics & numerical data*; D000328:Adult; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D005260:Female; D005684:Gait / Q000502:physiology; D006801:Humans; D049590:Postpartum Period / Q000502:physiology; D011187:Posture / Q000502:physiology; D011247:Pregnancy / Q000502:physiology*; D011434:Proprioception / Q000502:physiology*