Am J Perinatol
DOI: 10.1055/a-2097-1358
Original Article

Maternal Epidemiology of Brachial Plexus Birth Injuries in California: 1996 to 2012

1   Department of Orthopaedic Surgery, University of California Davis, Sacramento, California
2   Department of Orthopaedic Surgery, Shriners Hospitals for Children Northern California, Sacramento, California
Machelle D. Wilson
3   Department of Public Health Sciences, Division of Biostatistics, Clinical and Translational Science Center, University of California Davis, Sacramento, California
Barton L. Wise
4   Department of Internal Medicine, University of California Davis, Sacramento, California
Joy Melnikow
5   Department of Family and Community Medicine, University of California Davis, Sacramento, California
6   Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine University of California Davis, Sacramento, California
Michelle A. James
1   Department of Orthopaedic Surgery, University of California Davis, Sacramento, California
2   Department of Orthopaedic Surgery, Shriners Hospitals for Children Northern California, Sacramento, California
Daniel J. Tancredi
7   Department of Pediatrics, University of California Davis, Sacramento, California
› Author Affiliations
Funding This work was supported by the National Center for Advancing Translational Sciences, National Institutes of Health, through grant number UL1 TR001860 and linked award KL2 TR001859. The work was also supported by the Maternal and Child Health Bureau, Health Resources and Services Administration (HRSA) of the U.S. Department of Health and Human Services (HHS) award number R40MC375370100 totaling $100,000 with 0% financed with non-governmental sources.


Objective This study aimed to evaluate the incidence of brachial plexus birth injury (BPBI) and its associations with maternal demographic factors. Additionally, we sought to determine whether longitudinal changes in BPBI incidence differed by maternal demographics.

Study Design We conducted a retrospective cohort study of over 8 million maternal–infant pairs using California's Office of Statewide Health Planning and Development Linked Birth Files from 1991 to 2012. Descriptive statistics were used to determine BPBI incidence and the prevalence of maternal demographic factors (race, ethnicity, age). Multivariable logistic regression was used to determine associations of year, maternal race, ethnicity, and age with BPBI. Excess population-level risk associated with these characteristics was determined by calculating population attributable fractions.

Results The incidence of BPBI between 1991 and 2012 was 1.28 per 1,000 live births, with peak incidence of 1.84 per 1,000 in 1998 and low of 0.9 per 1,000 in 2008. Incidence varied by demographic group, with infants of Black (1.78 per 1,000) and Hispanic (1.34 per 1,000) mothers having higher incidences compared with White (1.25 per 1,000), Asian (0.8 per 1,000), Native American (1.29 per 1,000), other race (1.35 per 1,000), and non-Hispanic (1.15 per 1,000) mothers. After controlling for delivery method, macrosomia, shoulder dystocia, and year, infants of Black (adjusted odds ratio [AOR] = 1.88, 95% confidence interval [CI] = 1.70, 2.08), Hispanic (AOR = 1.25, 95% CI = 1.18, 1.32), and advanced-age mothers (AOR = 1.16, 95% CI = 1.09, 1.25) were at increased risk. Disparities in risk experienced by Black, Hispanic, and advanced-age mothers contributed to a 5, 10, and 2% excess risk at the population level, respectively. Longitudinal trends in incidence did not vary among demographic groups. Population-level changes in maternal demographics did not explain changes in incidence over time.

Conclusion Although BPBI incidence has decreased in California, demographic disparities exist. Infants of Black, Hispanic, and advanced-age mothers are at increased BPBI risk compared with White, non-Hispanic, and younger mothers.

Key Points

  • The incidence of BPBI has decreased over time.

  • Demographic disparities in BPBI incidence and risk exist.

  • Infants of Black, Hispanic, and advanced age mothers are at greatest risk of BPBI.

Supplementary Material

Publication History

Received: 09 December 2022

Accepted: 19 May 2023

Accepted Manuscript online:
22 May 2023

Article published online:
27 June 2023

© 2023. Thieme. All rights reserved.

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