Targeted sequencing of maternal plasma for haplotype-based non-invasive prenatal testing of spinal muscular atrophy.

Five pregnant women with a child affected by spinal muscular atrophy (SMA) were recruited between November 2014 and March 2015. Deletion of exons 7 and/or 8 in the SMN1 gene were identified by multiplex ligation-dependent probe amplification (MLPA), the current standard diagnostic test for SMA. Parental and fetal haplotypes of the SMN1 gene were determined in each family from haplotype-based non-invasive testing of blood samples and maternal plasma, respectively. Fetal haplotype was compared with the results of MLPA of fetal DNA obtained from amniotic fluid or chorionic villi. Parental haplotypes were constructed successfully in the five families. Assisted by the information on parental haplotype, non-invasive testing of maternal plasma identified one fetus with homozygous deletion of exons 7 and 8, two fetuses with heterozygous deletion of exons 7 and 8 and two normal fetuses. These results were consistent with the diagnosis by MLPA. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.