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Mapping Worldwide Incidence of Brachial Plexus Birth Injury: Preliminary Meta-Analytic Grounds for a Genetic Contribution
Holly Cordray, BS
1, Miguel Fiandeiro, BA
1, Seungjun Lee, BA
2, Roger Cornwall, MD
3, Petra Grahn, MD
4, Marja Kaijomaa, MD
5, M. Claire Manske, MD
6, Melissa Previtera, MA
7; Apurva S. Shah, MD, MBA
8(1)Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, (2)Boston University Chobanian & Avedisian School of Medicine, Boston, MA, (3)Cincinnati Children's Hospital Medical Center, Cincinnati, OH, (4)New Children's Hospital, Helsinki University Hospital, University of Helsinki, Helsinki, Finland, (5)Women's Hospital, Helsinki University Hospital, University of Helsinki, Helsinki, Finland, (6)Shriners Hospital for Children Northern California, Sacramento, CA, (7)Health Sciences Library, University of Cincinnati, Cincinnati, OH, (8)Children's Hospital of Philadelphia, Philadelphia, PA
Introduction: Brachial plexus birth injury (BPBI) transiently or permanently disables the neonatal upper extremity. More than half of cases occur without prenatally identifiable risk factors. This meta-analysis aimed to map geographically based differences in BPBI incidence worldwide as a preliminary step toward investigating potential population-level risk factors.
Materials & Methods: This systematic review searched PubMed, Embase, Cochrane, and Web of Science. Non-English-language articles were reviewed using machine translation. Eligible studies provided cross-sectional data on BPBI incidence without inclusion criteria predicated on known fetal/maternal risk factors, excluding review articles. Following PRISMA guidelines, two reviewers screened studies, extracted data, and assessed risk of bias using the Joanna Briggs Institute tools. Meta-analyses of proportions were conducted using random-effects models to estimate global incidence; covariates were incorporated with meta-regressions to compare population-based differences.
Results: Reviewers screened 1245 studies and 121 were included. All met quality assessment criteria. Sixteen studies used duplicate data; the pool was consolidated to 109 studies to avoid over-representing certain cohorts. The pooled global sample captured 74.7 million live births, representing 33 countries across all six populated continents. After addressing sampling bias by excluding studies limited to operative deliveries, breech presentation, or cephalic presentation, 86 studies totaling 71.2 million births yielded a pooled global BPBI incidence of 1.5 per thousand births (95% CI: 1.3-1.7). Meta-regression analyzing country of birth as a moderator showed significant regional differences in BPBI incidence (
P < .001); country of birth explained 48.0% of between-study variance. Figure 1 illustrates international variation in BPBI incidence, and Table 1 provides population-level results. Distributions of known risk factors were compared as balancing measures. From 34 studies that tracked permanent BPBI, 17.9% (95% CI: 15.2-21.0%) of BPBI cases persisted beyond one year of life.
Conclusions: Significant geographically based variation in BPBI incidence warrants exploration of population-level influences, including potential genetic contributions. These results complement earlier evidence on obstetric factors and social determinants of health, beginning to address remaining unpredictability that known risk factors cannot explain. Additional studies of South American, African, and Northeast Asian epidemiology would address a gap in the literature.
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