Anthropometry, standing posture, and body center of mass changes up to 28 weeks postpartum in Caucasians in the United States.

Background: Anthropometric models are used when body center of mass motion is calculated for assessment of dynamic balance. It is currently unknown how body segments and posture change in the postpartum period. Therefore, this study was conducted to evaluate the longitudinal changes in anthropometry, center of mass, and standing posture postpartum.

Methods: Seventeen pregnant women were tested at nine different times: 16-20 weeks and 36-40 weeks gestation, and then in 4-week intervals from childbirth to 28 weeks postpartum. Anthropometry was measured and then participants conducted a static standing and static laying trial. Force plate data and motion capture data were used in combination with anthropometry to calculate the masses of individual segments and the body center of mass. Change over time was determined through a linear mixed model analysis.

Results: Anthropometric changes related to the abdomen or fluid retention during pregnancy immediately regress to early pregnancy levels following childbirth. However, other changes related to breast tissue and fat deposits persist postpartum. As such, masses of different segments affect an anthropometric model for center of mass calculation, and body center of mass changes in the lateral and anterior directions postpartum. Vertical body center of mass position was unaffected.

Significance: Increased postpartum breast mass may be the cause of persistent lordotic curvature changes in the lumbar spine. There is potential that this affects postpartum back pain. Future research should explore how body center of mass changes postpartum for individuals that do not breast feed, and thus may not have significant breast mass postpartum.