Brachial plexus injury causation in newborns debated
Certain brachial plexus injuries during the birth process are unpreventable and are caused by etiologies other than shoulder dystocia.
- Some BPP is not the result of lateral traction on the shoulder during diffi cult deliveries.
- Fetal malpresentation, congenital or acquired maternal uterine defects, and strong maternal expulsive forces may cause the injury to the nerve plexus.
- Risk factors for shoulder dystocia include maternal obesity, diabetes, and postterm pregnancy, all linked to macrosomia, as well as labor induction and epidural anesthesia.
- McRobert's maneuver, suprapubic pressure, rotational maneuvers, and delivery of the posterior arm have all been used with varying degrees of success in relieving shoulder dystocia.
There is little doubt that strong lateral traction or rotation of the fetal head can tear or stretch the fetal brachial plexus, resulting in permanent or temporary paralysis, respectively. If true shoulder dystocia exists (which we define as a fetal shoulder obstructed for more than 1 minute), the birth attendant must use all the recommended manipulations described in most obstetric textbooks in an attempt to alleviate the anterior shoulder from behind the symphysis pubis of the mother. No single maneuver appears more successful or less prone to brachial plexus paralysis than another, and there is no specific order in which to perform these procedures.21 However, even meticulous completion of these maneuvers, with release of the impacted shoulder, will not guarantee the absence of BPP.
How does one measure the level of traction to assure that excessive force is not exerted? We know that the amount of pressure varies with each practitioner. We also know that the amount of force produced by the uterus during contractions varies widely. Further, we know that the amount of force produced by the pushing effort varies widely per person and per pushing attempt. It has also been shown that individual fetal brachial plexuses avulse and stretch in response to different amounts of force.
Thus, it is impossible to determine the exact amount of traction required to cause injury or whether it occurred before or after the caregiver attempted to relieve the dystocia. In short, although plaintiffs' attorneys in brachial plexus injury cases may argue that BPP always reflects negligence, this is simply untrue. We recommend that continued research focus on the etiologies of BPP, integrating the science of physics to determine the safest method of delivering a healthy infant in spite of shoulder dystocia.
DR ROSENMAN is associate clinical professor, Yale University School of Medicine, New Haven, Connecticut. MS SACCO is an attorney at Danaher, Lagnese & Sacco, PC, Hartford, Connecticut. MR SHARIFI is a medical student at Yale University School of Medicine, New Haven.
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