Nationwide Implementation of Newborn Screening for Spinal Muscular Atrophy in Canada.

BACKGROUND AND

OBJECTIVES

Newborn screening (NBS) for spinal muscular atrophy (SMA) and reimbursement of disease-modifying therapies (DMTs) are managed provincially in Canada, creating inequities in diagnosis and treatment. We describe NBS methodology, reporting practices, and DMT reimbursement across Canada and report the first national birth prevalence of SMA.

METHODS

We conducted a cross-sectional survey of laboratory directors from each provincial NBS program, validated against publicly available government sources (censored December 31, 2025). Birth prevalence was calculated using a Poisson 95% CI. The study met research ethics board deferral criteria as a quality assurance study.

RESULTS

Since NBS initiation (Ontario, in January 2020; full national coverage, in August 2024), 1,502,890 infants were screened. Of the 120 infants reported to have homozygous absence of exon 7 in SMN1, the estimated national birth prevalence was 1 in 12,524 births (95% CI 1:10,554 to 1:15,245 births). The distribution of SMN2 copy numbers in newborns with SMA identified 2 newborns (1.7%) with one copy of SMN2, 51 (42.5%) with 2 copies of SMN2, 41 (34.2%) with 3 copies of SMN2, 23 (19.2%) with 4 copies of SMN2, and 3 (2.5%) with 5 copies of SMN2. First-tier testing methodology and second-tier confirmation varied by province, as did the timing of SMN2 copy number availability at first family contact. DMT reimbursement for infants with 4 copies of SMN2 is not nationally harmonized.

DISCUSSION: Canada achieved universal SMA screening in August 2024; however, interprovincial variability persists in testing methodology, SMN2 copy number reporting, and DMT access. Infants with 4 copies of SMN2 face particularly inequitable treatment access despite growing expert consensus supporting early treatment initiation. Ongoing work is needed to eliminate inequity in regional drug reimbursement criteria for Canadian newborns identified with SMA on NBS.