Static Trunk Posture in Sitting and Standing During Pregnancy and Early Postpartum Wendy L. Gilleard, PhD, Jack Crosbie, PhD, Richard Smith, PhD ABSTRACT. Gilleard WL, Crosbie J, Smith R. Static trunk posture in sitting and standing during pregnancy and early post- partum. Arch Phys Med Rehabil 2002;83:1739-44. 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 univer- sity. Participants: A volunteer convenience sample of 9 primi- parous and multiparous women and 12 nulliparous women serving as a control group. Interventions: Not applicable. Main Outcome Measures: Subjects were filmed while sit- ting and during quiet standing at intervals throughout preg- nancy and at 8 weeks postpartum. A repeated-measures anal- ysis 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. Key Words: Postpartum period; Posture; Pregnancy; Reha- bilitation; Spine. © 2002 by the American Congress of Rehabilitation Medi- cine and the American Academy of Physical Medicine and Rehabilitation S TANDING AND SITTING are 2 common daily postural tasks that continue to be performed during pregnancy. Approximately 50% of pregnant women report back pain, 1 and changes in standing lumbar posture during pregnancy have been related to back pain by some investigators. 1,2 Pregnancy is associated with increased mass and circumferences, particu- larly in the trunk, which may influence these postures. Studies of quiet standing postures as pregnancy progresses have shown equivocal results. Alterations in pelvic inclination 3 and in lum- bar 4-9 and thoracic curvatures 4,5,8,9 have been reported. Reports differ as to whether there is an increase or decrease in lumbar curvature, and the extent of changes in curvatures is also debated. Some investigations have reported no significant change in pelvic inclination, 4 sacral base inclination, 3 thoracic kyphosis, 3,6,7 or lumbar lordosis. 1 The use of different study designs and measurement techniques makes comparison of these studies difficult. Moore et al 7 and Bullock-Saxton 5 have also reported that individual subjects showed different postural behaviors, with some increasing and some decreasing their lumbar lordosis. Postural adaptations in quiet standing may therefore be individual in nature. Pregnancy has been shown to affect trunk and arm posture during a seated typing task. 10,11 The changes seen, however, may have resulted from the constraints of the workspace rather than being an effect of pregnancy on the sitting posture. In sitting, the increasing size of the lower trunk and its apposition with the thighs may restrict the anterior tilt of the pelvis and thus affect the posture of other trunk segments. The effect of increasing trunk dimensions on the upper-body segments’ pos- tural alignment in the sagittal plane during sitting is not known. Postpartum, the gravid uterus and its contents no longer influence the maternal musculoskeletal system. It therefore may be logical to assume that any adaptations that have oc- curred will be reversed. Reversal of adaptations to preg- nancy, however, may not be complete in the early postpartum period. 5,8,12 Any effects of pregnancy on posture, therefore, may persist after the delivery 6 and may be detrimental to the normal functions of the trunk musculoskeletal system. In ad- dition, during the early postpartum period, there is a rapid increase in the number of lifting and carrying tasks undertaken within normal daily activities, with a subsequent increase in trunk tissue loads. Any ongoing changes in trunk posture may exacerbate the effects of increases in tissue loads. This study investigated the alignment of the upper body in the sagittal plane during sitting and standing as pregnancy progressed and in the early postpartum period. It is possible that changes attributed to pregnancy are actually related to normal variations in human subjects, which occur over time or result from repeated testing. Nulliparous subjects were there- fore used as control subjects to establish the consistency of the data over a time period similar to that used for data collection in maternal subjects. METHODS Nine maternal women (age range, 28 – 40y; height, 154 – 172.5cm; postpartum test mass, 51– 81kg) and 12 nulliparous women (age range, 21–35y; height, 160 –176.5cm; mass at third test, 52–75.5kg) volunteered and were included in the study, which was approved by the University of Sydney Ethics Committee. Maternal subjects included 5 primigravidas and 4 multigravidas. The maternal group was tested at 18 weeks or less, 24 weeks, 32 weeks, and 38 weeks of gestation and again at 8 weeks postpartum (maternal sessions 1–5). The control From the School of Exercise Science and Sport Management, Southern Cross University, Lismore, Australia (Gilleard); and the University of Sydney, Sydney, Australia (Crosbie, Smith). No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated. Correspondence to Wendy L. Gilleard, PhD, School of Exercise Science and Sport Management, Southern Cross University, PO Box 157, Lismore, 2480, NSW, Aus- tralia, e-mail: wgillear@scu.edu.au. Reprints are not available. 0003-9993/02/8312-7272$35.00/0 doi:10.1053/apmr.2002.36069 1739 Arch Phys Med Rehabil Vol 83, December 2002