Postpartum biomechanical adaptations of the anterior abdominal wall in a rat model: Implications for diastasis rectus abdominis

This study used a rat model to characterize postpartum biomechanical adaptations of the central anterior abdominal wall, including tissue containing the linea alba, and to explore implications for diastasis rectus abdominis. Samples were collected from nulliparous, 3-day postpartum, and 8-week postpartum Sprague-Dawley rats at upper, middle, and lower abdominal regions centered on the linea alba. Tensile testing showed that tissue from 3-day postpartum animals had significantly higher yield stress and maximum stress than both nulliparous and 8-week postpartum groups, with a similar near-significant trend toward higher Young’s modulus. By 8 weeks postpartum, the mechanical response had returned toward nulliparous levels. Histology showed greater inter-rectus distance in the early postpartum group, while connective tissue thickness between the rectus muscles remained similar to nulliparous controls, suggesting expansion and reorganization rather than simple thinning. Overall, the study indicates that pregnancy induces substantial but time-dependent remodeling of the anterior abdominal wall, with early postpartum strengthening and stiffening that may reflect an adaptive response rather than immediate tissue weakening.