Case report of pregnancy management and genetic evaluation after negative carrier screening for spinal muscular atrophy in an affected family

BACKGROUND: Screening for spinal muscular atrophy (SMA) is recommended for all pregnant women; however, interpreting the results of carrier screening in the context of family history can be challenging. CASE: We report the case of a 28-year-old woman (G4P3001) with two previous children affected with SMA and negative carrier screening via the Horizon 4 panel. SMN1/2 analysis was pursued to clarify risk for point mutations, carrier screening for her partner, and diagnostic testing for the fetus for SMA. Results of this testing confirmed her status as a silent carrier for SMA and the status of the fetus. CONCLUSION: Carrier screening does not account for family history and can therefore generate results inconsistent with known inheritance patterns. In these situations, additional genetic testing and genetic counseling are indicated to clarify risk for SMA in pregnancy and guide prenatal and neonatal healthcare.