Epidemiology of Brachial Plexus Birth Injury and the Impact of Cesarean Section on Its Incidence

Abstract

Background: While prior research provided thorough analysis of the epidemiology of brachial plexus birth injury (BPBI) from 1997 to 2012, recent trends are unknown. The goal of this study was to update the understanding of the epidemiology and risk factors for BPBI. Methods: Installments of the Kids’ Inpatient Database (1997 to 2019) were used to estimate BPBI incidence in the United States in comparison to several independent variables over time. An interaction between cesarean (C-) section and newborn weight was explored by defining BPBI rates in a stratified manner. A logistic regression model accounting for this interaction was developed to produce odds ratios for independent factors. Lastly, the temporal relationship between BPBI rates and C-section rates was explored using linear regression. Results: BPBI rates were steady around 0.9 to 1.1 per 1000 live births between 2006 and 2019. C-section rates were similarly stable between 32.3% and 34.0% over this period. Stratified analysis indicated C-section delivery was protective against BPBI across newborn weight classes, but the magnitude of this protective value was highest among newborns with macrosomia. Shoulder dystocia was the strongest risk factor for BPBI in the logistic regression model [adjusted odds ratio (AOR): 56.9, P<0.001]. The AOR for a newborn with macrosomia born through C-section (AOR: 0.581, 95% CI: 0.365-0.925) was lower than that for a normal weight newborn born vaginally (AOR: 1.000, P=0.022). Medicaid insurance coverage (AOR: 1.176, 95% CI: 1.124-1.230, P<0.001), female sex (AOR: 1.238, 95% CI: 1.193-1.283, P<0.001), and non-White race (AOR: 1.295, 95% CI: 1.237-1.357, P<0.001) were independent risk factors for BPBI. Over time, the rate of BPBI correlated very strongly with the rate of C-section (R 2=0.980). Conclusions: While BPBI and C-section rates were relatively stable after 2006, BPBI incidence strongly correlated with C-section rates. This highlights the need for close surveillance of BPBI rates as efforts to lower the frequency of C-section evolve. Female, Black, and Hispanic newborns and children with Medicaid insurance experience BPBI at a higher rate, a finding which could direct future research and influence policy. Level of Evidence: Level IV—case series.