Static trunk posture in sitting and standing during pregnancy and early postpartum

Objective: To investigate the postural alignment of the upper body in the sagittal plane during sitting and standing postures as pregnancy progressed and then in the postpartum period. Design: Longitudinal, repeated-measures design. Setting: Biomechanics laboratory in an Australian university. Participants: A volunteer convenience sample of 9 primiparous and multiparous women and 12 nulliparous women serving as a control group. Interventions: Not applicable. Main Outcome Measures: Subjects were filmed while sitting and during quiet standing at intervals throughout pregnancy and at 8 weeks postpartum. A repeated-measures analysis of variance was used to assess systematic changes in the alignment of the pelvic, thoracic, and head segments, and the thoracolumbar and cervicothoracic spines. Student t tests were used to compare the postpartum and nulliparous control groups. Results: There was no significant effect of pregnancy on the upper-body posture, although there was a tendency in some subjects for a flatter thoracolumbar spinal curve in sitting as pregnancy progressed. Postpartum during standing, the pelvic segment had a reduced sagittal plane anterior orientation, and the thoracolumbar spine was less extended, indicating a flatter spinal curve compared with the control group. Conclusions: There was no significant effect of pregnancy on upper-body posture during sitting and standing, although individuals varied in their postural response. A flatter spinal curve was found during standing postpartum.