Elective preterm birth for earlier spinal muscular atrophy treatment.

Spinal muscular atrophy is a severe neuromuscular disorder in which early treatment significantly improves outcomes. Prenatal diagnosis, particularly in fetuses with two SMN2 copies, presents unique challenges. We report a late-preterm infant diagnosed in utero with homozygous SMN1 deletion and two SMN2 copies, whose older sibling developed motor deficits despite early postnatal treatment. Following multidisciplinary consultation, delivery was planned at 35+4 weeks to enable immediate therapy. The infant received oral risdiplam on day 2 of life, followed by intravenous onasemnogene abeparvovec on day 59. Neurofilament light-chain levels were normal at birth and remained low, except for a transient rise after gene therapy. Initial motor development was normal until 2 months, when hypotonia appeared, followed by recovery and normalization by 5 months. This case suggests that planned preterm delivery with rapid postnatal treatment may be a pragmatic alternative to in utero therapy for high-risk spinal muscular atrophy, pending further longitudinal data.