Impact of Pregnancy and Vaginal Delivery on the Passive and Active Mechanics of the Rat Vagina |
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Authors: | Andrew?Feola Pamela?Moalli Marianna?Alperin Robbie?Duerr Robin?E?Gandley Email author" target="_blank">Steven?AbramowitchEmail author |
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Institution: | (1) Musculoskeletal Research Center, Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA;(2) Magee-Womens Research Institute, Departments of Obstetrics and Gynecology and Reproductive Sciences, University of Pittsburgh, Pittsburgh, PA, USA; |
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Abstract: | Remodeling of vaginal extracellular matrix and smooth muscle likely plays a critical role in reducing the risk of maternal
injury during vaginal delivery by altering the mechanical properties to increase distension and reduce stress. Long-Evans
rats were divided into five groups to examine the passive mechanical and active contractile properties throughout pregnancy
and postpartum: virgin (n = 17), mid-pregnant (Day 14–16, n = 12), late-pregnant (Day 20–22, n = 14), immediate postpartum (0–2 h after delivery, n = 14), and 4 week postpartum (n = 15). Longitudinal sections of vaginal tissue were loaded to failure uniaxially for passive mechanical or active contractile
properties were examined. For passive mechanics, the tangent modulus decreased 45% by mid-pregnancy and immediately postpartum
(p < 0.001). The ultimate strain continuously increased up to 43% higher than virgin animals (p = 0.007) in the immediate postpartum group. For active mechanics, the maximal contractile force was 36–56% lower through
immediate postpartum animals, and was significantly more sensitive to K+ throughout pregnancy and postpartum (p = 0.003). The changes observed in the passive and active properties of the rat vagina are consistent with what would be expected
from a tissue that is remodeling to maximize its ability to distend at the time of vaginal delivery to facilitate passage
of the fetus with minimal injury. |
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