Spinal Muscular Atrophy: Inheritance, Screening, and Counseling for the Obstetric Provider

Importance Spinal muscular atrophy (SMA) confers significant risk of neonatal and infant morbidity and mortality. Screening women during or before pregnancy for carrier status of SMA presents an opportunity to identify pregnancies at risk for this potentially devastating condition. Objective The objective of this review is to describe the different forms of SMA and their inheritance. In addition, this review guides obstetric providers in interpreting results of carrier screening. Evidence Acquisition A MEDLINE search of “prenatal genetic testing,” “spinal muscular atrophy,” and “inheritance of spinal muscular atrophy” in the review was performed. Results The evidence cited in this review includes 4 medical society committee opinions and 14 additional peer-reviewed journal articles that were original research or expert opinion summaries. Conclusions and Relevance Spinal muscular atrophy is a severe, heterogeneous neurodegenerative disorder. The American College of Obstetricians and Gynecologists recommends that obstetricians offer carrier screening for SMA to all pregnant women. Given the different types and inheritance of SMA, understanding of the disease and interpreting carrier screening results is of paramount importance to the prenatal care provider. Target Audience Obstetrician-gynecologist, family medicine, or other practitioner(s) providing prenatal care. Learning Objectives After participating in this activity, physicians should be better able to identify indications for carrier testing for SMA; compare types of SMA based on age of onset and phenotype; interpret results of SMA carrier screening; counsel patients regarding residual risk after negative SMA carrier screening; and refer patients with positive SMA carrier screening.