Simulation of Pregnancy-Related Abdominal Mass Results in Nonimmediate Changes in Postural Control: An Exploratory Study

Background: Changes to segmental inertial properties, abdominal growth, and increased circulating relaxin are some of the numerous contributing factors to higher risks of falling during pregnancy. These factors emerge in different phases of pregnancy, have a cumulative effect, and vary across women. For these reasons, determining each factor's role in the development of higher fall risk is challenging and yet crucial in uncovering their clinical importance. Objectives: To investigate the independent effect of additional abdominal weight on balance control in nonpregnant women. Study Design: A longitudinal study. Methods: Ten healthy women were submitted to computerized posturography while an additional abdominal weight (7% of body mass) was applied for 24 hours. Postural behavior was recorded from 4 experimental conditions: before placement of the additional weight (Baseline), immediately after placement of the abdominal weight (T1), 24 hours after continuous application of the abdominal weight (T2), and immediately after abdominal weight removal (T3). Variables of interest were extracted from the participant's body sway dynamics and included the center of pressure (COP) migration area, range, root mean square (RMS), mean velocity, median frequency (F50), and signal sample entropy (SEnt). Results: At T3, significant increases were found for the COP migration area, mediolateral range, and mediolateral RMS (P values range: .005-.013). Also at T3, significant decreases were found for mediolateral F50 and SEnt (P values range: .001-.038). Conclusion: Modifications in balance behavior were observed when the abdominal weight was removed after 24 hours of application. Significant changes occurred in the mediolateral body sway amplitude and regularity suggesting the presence of mediolateral instability.