Background and Purpose. The purpose of this study was to investigate the abdominal muscle structural adaptations and functional capabilities during pregnancy and the postbirth period.
Subjects. Six primigravid subjects, aged 28 to 33 years, participated in nine test sessions from 14 weeks of gestation to 8 weeks postbirth. Methods. At each test session, three-dimensional photography of abdominal skin markers was used to determine the gross morphology of a representative abdominal muscle, the rectus abdominis muscle. The functional capability of the abdominal muscle group was assessed on the ability of the muscle group to stabilize the pelvis against resistance.
Results. Increases were found in rectus abdominis muscle separation width, length, and angles of insertion as pregnancy progressed. Reversal in rectus abdominis muscle separation was found by 4 weeks postbirth. The ability to stabilize the pelvis against resistance was shown to be decreased as pregnancy progressed and remained compromised postbirth. Decrements in abdominal muscle function paralleled in time the structural adaptations, as pregnancy progressed. Continued functional deficits were found in parallel with incomplete resolution of structural adaptations postbirth.
Conclusion and Discussion. Abdominal muscle function is affected by structural adaptations that occur during pregnancy. Because our results showed that the ability to stabilize the pelvis against resistance is decreased during pregnancy and at least 8 weeks postbirth, abdominal muscle exercises should be chosen with care.