Maternal Birth-Related Neuromuscular Injury and Recovery: Phase IIMagnetic resonance imaging data suggest a strong relationship between childbirth and structural pelvic floorinjury, likely originating from stretch or crush of maternal tissues during the expulsive phase of labor. Thepelvic floor muscle most vulnerable to injury is the striated pubovisceral muscle (PVM); 11-20% of parouswomen demonstrate a muscle defect at a year postpartum. A link between this defect and pelvic floordisorders has been found in our preliminary studies; women with prolapse and incontinence have a 4 foldand2 fold- higher rate of PVM defects respectively. This finding offers a plausible causal link between pelvicfloor 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 PVMdefects overtime and differentiate: 1) neurogenic injury (degeneration overtime), 2) myogenic injury (earlyand permanent avulsion), or 3) fully recoverable injury. Injury type can then be correlated with obstetric riskfactors and functional recovery. This study's aims are to: 1) Establish the validity of factors used to identifywomen with greatest likelihood of PVM injury by estimating the probability of each injury outcome classifiedat 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 PVMinjuries are associated with vaginal births vs. pregnancy by comparing our 125 women who birthed vaginallyto 50 women who birthed by elective Caesarean. 3) Determine the extent to which an array of clinicalparameters 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 thestandard 6-week postpartum evaluation. We will classify putative injury types and correlate with risk factorsand functional parameters. We will try to address the knowledge gaps identified at the March 2006 NIHconvened State-of-the-Science Conference: Cesarean Delivery on Maternal Request, which highlighted theneed for understanding the mechanisms and risk factors for PVM injury. The short-term goal is new insightson injury mechanism. The long-term goal is prevention of and better treatment for pelvic floor disorders.
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