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

Department of Obstetrics and Gynecology, Hospital Sant Pau, Universitat Autonoma de Barcelona, Spain.

The journal of maternal-fetal & neonatal medicine : the official journal of the European Association of Perinatal Medicine, the Federation of Asia and Oceania Perinatal Societies, the International Society of Perinatal Obstetricians 2012 Aug

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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. 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. 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. 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.

Citation

Juan Parra, Laura Alias, Eva Also-Rallo, Rebeca Martínez-Hernández, Raquel Senosiain, Carmen Medina, Obdulia Alejos, Noelia Rams, María Amenedo, Filomena Ormo, María Jesús Barceló, Joaquim Calaf, Montserrat Baiget, Sara Bernal, Eduardo F Tizzano. Evaluation of fetal nuchal translucency in 98 pregnancies at risk for severe spinal muscular atrophy: possible relevance of the SMN2 copy number. The journal of maternal-fetal & neonatal medicine : the official journal of the European Association of Perinatal Medicine, the Federation of Asia and Oceania Perinatal Societies, the International Society of Perinatal Obstetricians. 2012 Aug;25(8):1246-9