Our understanding of the mechanisms of maternal pelvic skeletal muscle birth injury is limited, and what is known is mainly derived from the indirect studies. Importantly, it remains unclear what separates women who sustain pelvic muscle injury from those who do not. To address this question, we study pregnancy-induced adaptations in an experimental model, which allows for longitudinal follow up and direct tissue- and cellular-level investigations. Using this model, we discovered that under the physiologic conditions of pregnancy, pelvic floor muscles show remarkable plasticity. Specifically, pelvic muscles adapt to their new environment by increasing fiber length via the addition of sarcomeres (muscle functional units) and intramuscular collagen content in preparation for delivery. We went on to demonstrate that these pregnancy-induced adaptations protect pelvic floor muscles from maternal birth injury! We are currently exploring the effects of pregnancy and birth injury on biochemical, biomechanical, and stem cell properties of pelvic floor muscles. These studies will advance our understanding of the mechanisms of maternal birth injury and identify potential screening and therapeutic targets that will enable us to identify women at risk of maternal pelvic floor muscle injury.