Maternal Birth-Related Neuromuscular Injury and Recovery: Phase II Magnetic resonance imaging data suggest a strong relationship between childbirth and structural pelvic floor injury, likely originating from stretch or crush of maternal tissues during the expulsive phase of labor. The pelvic floor muscle most vulnerable to injury is the striated pubovisceral muscle (PVM);11-20% of parous women demonstrate a muscle defect at a year postpartum. A link between this defect and pelvic floor disorders has been found in our preliminary studies;women with prolapse and incontinence have a 4 foldand 2 fold- higher rate of PVM defects respectively. This finding offers a plausible causal link between pelvic floor disorders and a structural injury that occurs at childbirth. The cause of the defect is not yet known; nerve or muscle injury might be the underlying mechanism. Serial MRI offers the ability to observe PVM defects overtime and differentiate: 1) neurogenic injury (degeneration overtime), 2) myogenic injury (early and permanent avulsion), or 3) fully recoverable injury. Injury type can then be correlated with obstetric risk factors and functional recovery. This study's aims are to: 1) Establish the validity of factors used to identify women with greatest likelihood of PVM injury by estimating the probability of each injury outcome classified at 6 months postpartum in a sample (n=125) enriched for risk factors of long duration of 2nd stage, instrumented delivery, 3rd or 4th degree perineal lacerations, macrosomic infant. 2) Establish that PVM injuries are associated with vaginal births vs. pregnancy by comparing our 125 women who birthed vaginally to 50 women who birthed by elective Caesarean. 3) Determine the extent to which an array of clinical parameters observed at 6 weeks postpartum will predict long term (6 months) muscle outcomes. To do so, we will obtain MRI's at 2 weeks and 6 months postpartum and perform functional PVM testing at the standard 6-week postpartum evaluation. We will classify putative injury types and correlate with risk factors and functional parameters. We will try to address the knowledge gaps identified at the March 2006 NIH convened State-of-the-Science Conference: Cesarean Delivery on Maternal Request, which highlighted the need for understanding the mechanisms and risk factors for PVM injury. The short-term goal is new insights on injury mechanism. The long-term goal is prevention of and better treatment for pelvic floor disorders.

National Institute of Health (NIH)
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
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University of Michigan Ann Arbor
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