Preimplantation genetic diagnosis for chromosomal rearrangements with the use of array comparative genomic hybridization at the blastocyst stage

Abstract

Objective: To establish the value of array comparative genomic hybridization (CGH) for preimplantation genetic diagnosis (PGD) in embryos of translocation carriers in combination with vitrification and frozen embryo transfer in nonstimulated cycles.

Design: Retrospective data analysis study.

Setting: Academic centers for reproductive medicine and genetics.

Patient(s): Thirty-four couples undergoing PGD for chromosomal rearrangements from October 2013 to December 2015.

Intervention(s): Trophectoderm biopsy at day 5 or day 6 of embryo development and subsequently whole genome amplification and array CGH were performed.

Main outcome measure(s): This approach revealed a high occurrence of aneuploidies and structural rearrangements unrelated to the parental rearrangement. Nevertheless, we observed a benefit in pregnancy rates of these couples.

Result(s): We detected chromosomal abnormalities in 133/207 embryos (64.2% of successfully amplified), and 74 showed a normal microarray profile (35.7%). In 48 of the 133 abnormal embryos (36.1%), an unbalanced rearrangement originating from the parental translocation was identified. Interestingly, 34.6% of the abnormal embryos (46/133) harbored chromosome rearrangements that were not directly linked to the parental translocation in question. We also detected a combination of unbalanced parental-derived rearrangements and aneuploidies in 27 of the 133 abnormal embryos (20.3%).

Conclusion(s): The use of trophectoderm biopsy at the blastocyst stage is less detrimental to the survival of the embryo and leads to a more reliable estimate of the genomic content of the embryo than cleavage-stage biopsy. In this small cohort PGD study, we describe the successful implementation of array CGH analysis of blastocysts in patients with a chromosomal rearrangement to identify euploid embryos for transfer.

Keywords: Preimplantation genetic diagnosis (PGD); array CGH; blastocysts; chromosomal rearrangements; trophectoderm biopsy.