The broad, long-term objectives of the Neuromuscular Injury and Recovery after Vaginal Delivery project are 1) to document the specific labor event or combination of events associated with the greatest evidence of short and long term neuromuscular maternal injury, and 2) to determine differences in these injury mechanisms between minority and Caucasian women. Immediate specific aims of this longitudinal study are: 1) documenting normal neuromuscular function and radiologic anatomy of pelvic and perineal muscles in nulliparous African-American and Hispanic women, 2) identifying, enrolling, and following a cohort of 135 primigravid women of representative ethnic groups to participate in antepartum, intrapartum, and postpartum electromyographic studies of pelvic and perineal muscle function, 3) studying the effects of epidural analgesia on striated muscle of maternal pelvis and perineum, and 4) comparing magnetic resonance imaging (MRI) studies of the pelvic anatomy of these women and correlating those findings to the functional EMG findings. These studies will provide a greater understanding of the mechanism of maternal pelvic injury at the time of vaginal delivery, which is the single greatest contributor to the risk of developing urinary incontinence (UI) and pelvic floor dysfunction (PFD). Furthermore, we will help close a gap in our significant knowledge deficit regarding racial differences in female pelvic floor function. The first phase of the study will involve the recruitment of nulliparous African-American and Hispanic women to establish normative values of pelvic musculature for that group via quantitative electromyography (QEMG) and pelvic MRI. This data, and normative data in Caucasian women from previous studies, will be used for the second phase of the study, which will study events in women of diverse racial backgrounds undergoing their first vaginal delivery. In this phase, primigravid subjects will undergo ~QEMG exam in the third trimester, again immediately prior to the second stage of labor, one day or two days postpartum, and 6 months postpartum. Precise measures of intrapartum events, including the descent of the fetal head in the pelvis, and time to actual delivery, will allow correlation with QEMG data. During the intrapartum phase, subjects will undergo QEMG exam before and after the placement of epidural analgesia, to precisely document the effect of epidural on the function of striated muscles of the pelvis. These subjects will also undergo pelvic MRI studies to provide anatomic correlation with functional QEMG data.
