BackgroundThe majority of human embryos created using in vitro fertilisation (IVF) techniques are aneuploid. Comprehensive chromosome screening methods, applicable to single cells biopsied from preimplantation embryos, allow reliable identification and transfer of euploid embryos. Recently, randomised trials using such methods have indicated that aneuploidy screening improves IVF success rates. However, the high cost of testing has restricted the availability of this potentially beneficial strategy. This study aimed to harness next-generation sequencing (NGS) technology, with the intention of lowering the costs of preimplantation aneuploidy screening.MethodsEmbryo biopsy, whole genome amplification and semiconductor sequencing.ResultsA rapid (<15 h) NGS protocol was developed, with consumable cost only two-thirds that of the most widely used method for embryo aneuploidy detection. Validation involved blinded analysis of 54 cells from cell lines or biopsies from human embryos. Sensitivity and specificity were 100%. The method was applied clinically, assisting in the selection of euploid embryos in two IVF cycles, producing healthy children in both cases. The NGS approach was also able to reveal specified mutations in the nuclear or mitochondrial genomes in parallel with chromosome assessment. Interestingly, elevated mitochondrial DNA content was associated with aneuploidy (p<0.05), a finding suggestive of a link between mitochondria and chromosomal malsegregation.ConclusionsThis study demonstrates that NGS provides highly accurate, low-cost diagnosis of aneuploidy in cells from human preimplantation embryos and is rapid enough to allow testing without embryo cryopreservation. The method described also has the potential to shed light on other aspects of embryo genetics of relevance to health and viability.
This study retrospectively analysed array comparative genomic hybridization (CGH) results of 7753 embryos from 990 patients to determine the frequency of embryonic euploidy and its relationship with the cohort size (i.e. the number of embryos available for biopsy and array CGH analysis). Linear regression analysis was performed to assess the effect of cohort size on euploidy rate adjusted for the effect of female age. While increasing female age was associated with a significant decrease in euploidy rate of day-3 and day-5 embryos (P<0.001 for both groups), cohort size was not significantly associated with euploidy rate. Logistic regression analysis was performed to assess the effect of cohort size, adjusted for maternal age, on the likelihood of having at least one euploid embryo available for transfer. The odds of having at least one euploid embryo in an assisted cycle was significantly decreased by increasing female age (P<0.01 for both day-3 and day-5 embryos) and was significantly increased by every additional embryo available for analysis (P<0.001 for both day-3 and day-5 embryos).
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