Prevention Unintentional Mechanical Birth Injuries

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The objective of this proposal is to elucidate mechanisms involved in mechanical birth injuries that occur following an obstetric emergency known as shoulder dystocia and to develop practical interventions to control or prevent such injuries, some of which can lead to lifelong disability. Affecting up to 15% of vaginal deliveries, shoulder dystocia is a naturally-occurring mechanical obstruction in which, after the head delivers, the fetal shoulders become impacted behind the mother's pubic bone and the trunk cannot deliver without specific intervention by the clinician who must act expediently to prevent asphyxia while simultaneously avoiding undue stretch on the fetal neck. The latter can result in skeletal fractures and/or brachial plexus nerve injury -- unintended outcomes of up to nearly 30% of shoulder dystocias. Standard obstetric maneuvers used to resolve shoulder dystocia involve manipulation of either the mother or the fetus. The superiority of one maneuver over another has not been proven; yet biomechanical considerations support the hypothesis that fetal manipulation requires 20% to 30% less force to deliver the infant than maternal manipulation and, if prioritized, could reduce the incidence of injury. However, most clinicians are less familiar with fetal maneuvers and defer their use in favor of repeating maternal ones. The goals of this research proposal are to demonstrate the mechanical advantage of fetal over maternal manipulation in accomplishing atraumatic resolution of shoulder dystocia and to familiarize clinicians with fetal maneuvers as a public health measure to reduce and prevent neonatal injury. To achieve these objectives, biomedical engineering will be integrated with clinical obstetrics through 5 specific aims: 1. to measure clinician-applied traction on the fetal head using a custom-designed shoulder dystocia birthing simulator and correlate direction, magnitude and rate of this force with fetal neck extension, flexion and rotation, brachial plexus stretch and skeletal fracture; 2. to objectively assess, in a laboratory setting, the effect of uterine and maternal expulsive forces and of different shoulder dystocia maneuvers on clinician-applied force, fetal neck motion parameters and brachial plexus stretch; 3. to conduct an educational program for clinicians on the performance of shoulder dystocia maneuvers, employing the laboratory simulator and force-measuring systems, and assess its effect on clinicians' ability to estimate the amount of traction they apply during delivery; 4. to measure clinician-applied traction in vivo and compare this with laboratory-derived force parameters; 5. to conduct a small, randomized clinical trial comparing clinician-applied forces following McRoberts' maneuver (a maternal manipulation) and following Rubin's maneuver (a fetal manipulation).