Evaluation of fetal nuchal translucency in 98 pregnancies at risk for severe spinal muscular atrophy: possible relevance of the SMN2 copy number

J Matern Fetal Neonatal Med. 2012 Aug;25(8):1246-9. doi: 10.3109/14767058.2011.636101. Epub 2011 Nov 30.

Abstract

Objective: To study fetal nuchal translucency (NT) thickness as a possible early marker in fetuses at risk for severe spinal muscular atrophy (SMA). To investigate the significance of the survival motor neuron (SMN) 2 gene copy number in affected fetuses.

Methods: We performed 2D-ultrasound in 98 pregnancies at risk for SMA, all of which underwent prenatal molecular testing of the SMN1 gene. Crown-rump length (CRL) and NT measurements were obtained in all cases before chorionic villus sampling. Fetuses were diagnosed as healthy, carriers or affected according to the SMN1 molecular testing results. SMN2 copies were also tested in all affected fetuses.

Results: Nineteen fetuses were predicted to be affected due to the absence of the SMN1 gene, 18 of which had two SMN2 copies. Mean CRL and NT values did not differ between healthy, carrier and affected fetuses. In the remaining affected case who had only one SMN2 copy, the ultrasound examination showed a NT value of 4.98 mm and findings compatible with hypoplastic left heart.

Conclusions: Most affected SMA fetuses have normal NT values. Our findings support the idea that SMN2 copy number in SMA fetuses is relevant for the development of congenital heart defects and increased NT values.

Publication types

  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cohort Studies
  • Crown-Rump Length
  • Female
  • Gene Dosage* / physiology
  • Genetic Predisposition to Disease
  • Genetic Testing / methods
  • Genetic Testing / statistics & numerical data
  • Humans
  • Muscular Atrophy, Spinal / diagnostic imaging*
  • Muscular Atrophy, Spinal / epidemiology
  • Muscular Atrophy, Spinal / genetics*
  • Nuchal Translucency Measurement* / statistics & numerical data
  • Pregnancy
  • Prenatal Diagnosis / methods
  • Risk Factors
  • Severity of Illness Index
  • Survival of Motor Neuron 2 Protein / genetics

Substances

  • SMN2 protein, human
  • Survival of Motor Neuron 2 Protein