Preimplantation genetic diagnosis for spinal muscular atrophy type I

Objective: Couples with children who have spinal muscular atrophy type I (SMA) face a 25% risk of having affected offspring with spontaneous conception. Preimplantation genetic testing (PGT) is possible for the deletions in the survival motor neuron (SMN) gene that have been identified in 98% of SMA type I cases. PGT would provide new reproductive options for families at risk for SMA. Methods: Three couples with previously affected children confirmed by DNA testing each underwent in vitro fertilization (IVF) and PGT of the resulting embryos. One or two blastomeres were biopsied from each embryo and analyzed for deletions in exons 7 and 8 of the SMN gene. Results: Nine embryos were predicted to be unaffected, three to be affected, and one embryo could not be interpreted. One of three patients receiving transfer of unaffected embryos became pregnant with twins. Conclusions: Preimplantation genetic testing provides a means for couples at risk for spinal muscular atrophy type I to reduce their chance of initiating an affected pregnancy.