Abstract
PurposeThe purpose of the study is to validate a method that provides the opportunity to distinguish a balanced translocation carrier embryo from a truly normal embryo in parallel with comprehensive chromosome screening (CCS).MethodsA series of translocation carrier couples that underwent IVF with single nucleotide polymorphism (SNP) array-based CCS on 148 embryos were included. Predictions of balanced or normal status of each embryo were made based upon embryonic SNP genotypes. In one case, microdeletion status was used to designate whether embryos were balanced or normal. In 10 additional cases, conventional karyotyping was performed on newborns in order to establish the true genetic status (balanced or normal) of the original transferred embryo. Finally, implantation potential of balanced or normal embryos was compared.ResultsPhasing SNPs using unbalanced embryos allowed accurate prediction of whether transferred embryos were balanced translocation carriers or truly normal in all cases completed to date (100 % concordance with conventional karyotyping of newborns). No difference in implantation potential of balanced or normal embryos was observed.ConclusionsThis study demonstrates the validity of a CCS method capable of distinguishing normal from balanced translocation carrier embryos. The only prerequisite is the availability of parental DNA and an unbalanced IVF embryo, making the method applicable to the majority of carrier couples. In addition, the SNP array platform allows simultaneous CCS for aneuploidy with the same platform and from the same biopsy. Future work will involve prospective predictions to select normal embryos with subsequent karyotyping of the resulting newborns.
Highlights
Very few causes of infertility or recurrent pregnancy loss can be explained by a clear genetic origin
The only prerequisite is the availability of parental DNA and an unbalanced in vitro fertilization (IVF) embryo, making the method applicable to the majority of carrier couples
Embryos that inherit an unbalanced karyotype can be readily identified through a variety of testing methods including fluorescence in situ hybridization, array comparative genomic hybridization, and single nucleotide polymorphism microarrays
Summary
Very few causes of infertility or recurrent pregnancy loss can be explained by a clear genetic origin. Chromosomal rearrangements represent one such cause with carrier patients experiencing an increased rate of failure to achieve a pregnancy and likelihood of having a miscarriage due to the unbalanced transmission of derivative chromosomes to gametes and offspring. Embryos that inherit an unbalanced karyotype can be readily identified through a variety of testing methods including fluorescence in situ hybridization, array comparative genomic hybridization, and single nucleotide polymorphism microarrays. The array-based methods of testing provide the added benefit of screening for whole chromosome aneuploidy of all 24 chromosomes (22 autosomes, X and Y) in parallel with the identification of unbalanced inheritance of chromosomes from the translocation [1,2,3,4,5]. Several randomized controlled trials have already demonstrated that comprehensive chromosome
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