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Abstract

We appreciate the comments of Allen with regard to our hypothesis that brachial plexus palsy can be an in utero event. The goal of our review article was to suggest that some cases of brachial plexus injury may be of intrauterine origin. Both the anterior brachial plexus and the posterior brachial plexus may be subject to significant degrees of in utero stretch, which is directly related to the pathophysiologic characteristics of shoulder dystocia itself. Although we agree that a “stretch” injury is the most likely mechanism of brachial plexus injury, compression of the brachial plexus by the symphysis pubis or uterine anomalies may also be etiologic. We disagree that there is considerable literature concerning the effect of intrauterine pressure or forces on the brachial plexus. We are unsure how Allen is able to scientifically conclude that the force needed to induce a temporary brachial plexus palsy is 22 lb. Allen appears to be drawing inferences from 2 cases of shoulder dystocia described in his cited reference 2. In this report a transient Erb’s palsy occurred in 1 case and no injury was pres-ent in the other. Not only did each of these macrosomic newborns have almost exactly the same birth weight, but they were delivered in the same amount of time and with the same peak force. Although the injured newborn was delivered with a slightly higher rate of force impulse and peak force rate, one is unable to make any sort of statistical comparison based on 2 cases. We therefore question the scientific validity of making wide-ranging inferences from this single case of brachial plexus injury. As acknowledged in our conclusion section, we recognize that the data referenced in our article are retrospective in nature. Although we concur that underreporting of difficult deliveries can occur, we continue to believe that “no shoulder” brachial plexus injuries are a distinct, real entity. We believe that most cases of shoulder dystocia and brachial plexus injury cannot be accurately predicted or prevented.1Lewis DF Edwards MS Asrat T Adair CD Brooks G London S. Can shoulder dystocia be predicted? Preconceptive and prenatal factors.J Reprod Med. 1998; 43: 654-658PubMed Google Scholar, 2Rouse DJ Owen J Goldenberg RL Cliver SP. The effectiveness and costs of elective cesarean delivery for fetal macrosomia diagnosed by ultrasound.JAMA. 1996; 276: 1480-1486Crossref PubMed Google Scholar We are unsure exactly what Allen means when he states “…perhaps reappraisal should focus more on…fully documenting shoulder dystocia.” Since when did an obstetrician’s failure to document shoulder dystocia prove to be causative for brachial plexus injury? We do, however, wholeheartedly welcome the efforts of Allen to help us further study the effects of intrauterine forces and objective diagnosis of shoulder dystocia. 6/8/102138