title: Risk factors for brachial plexus injury with and without shoulder dystocia.
abstract: OBJECTIVE
  To ascertain whether brachial plexus palsy (BPP) that occurs without shoulder dystocia (SD) represents a traction injury during unrecognized SD or a natural phenomenon with a different mechanism of injury, we compared risk factors and outcomes between SD-associated and non-SD-associated BPP.
  
  
  METHODS
  Neonates with BPP after cephalic vaginal delivery were pooled from all deliveries at Johns Hopkins (June, 1993-December, 2004) and a dataset of litigated permanent BPP from multiple institutions (1986-2003), grouped by SD association based on clinician documentation and compared by using Fisher exact and t tests.
  
  
  RESULTS
  Thirty percent of 49 non-SD-BPP and 11% of 280 SD-BPP lacked all risk factors for SD (P = .002). Compared with SD-BPP infants, non-SD-BPP infants were average weight (P < .001) and had cord pH less than 7.10 (P = .01) more commonly and exhibited a trend toward posterior shoulder involvement (P = .06). Nearly all non-SD-BPP were temporary, whereas more than 90% of permanent BPP were associated with SD (odds ratio 17, 7.3-39.6).
  
  
  CONCLUSIONS
  Non-SD-BPP is uncommon and likely mechanistically distinct from SD-BPP. Risk factors, birth weight, fetal acidosis, posterior arm involvement, and injury severity distinguish between shoulder dystocia-related brachial plexus injuries and those not recorded as such.
authors.affiliation: Department of Gynecology and Obstetrics, Johns Hopkins University, Baltimore, MD, USA.
authors.forename: Edith D
authors.initials: ED
authors.lastname: Gurewitsch
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Johnson
authors.forename: Sayeh
authors.initials: S
authors.lastname: Hamzehzadeh
authors.forename: Robert H
authors.initials: RH
authors.lastname: Allen
mesh_terms: D001917:Brachial Plexus / Q000293:injuries*; D002585:Cesarean Section / Q000706:statistics & numerical data; D036861:Delivery, Obstetric / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D009765:Obesity / Q000453:epidemiology; D010246:Paralysis, Obstetric / Q000453:epidemiology*; D011247:Pregnancy; D012307:Risk Factors; D000070599:Shoulder Injuries