Accurate detection and frequency of abnormal ploidy in the human blastocyst

Abstract

Objective: To validate the detection of abnormal ploidy in preimplantation embryos and evaluate its frequency in transferrable blastocysts.

Design: A high-throughput genome-wide single nucleotide polymorphism microarray-based preimplantation genetic testing (PGT) platform was validated using multiple positive controls, including cell lines of known haploid and triploid karyotypes and rebiopsies of embryos with initial abnormal ploidy results. This platform was then tested on all trophectoderm biopsies in a single PGT laboratory to calculate the frequency of abnormal ploidy and the parental and cell division origins of error.

Setting: Preimplantation genetic testing laboratory.

Patient(s): The embryos from in vitro fertilization patients who elected for PGT were evaluated. Any patients who provided saliva samples were further analyzed for the parental and cell division origins of abnormal ploidy.

Intervention(s): None.

Main outcome measure(s): Evaluable positive controls showed 100% concordance with original karyotypes. The overall frequency of abnormal ploidy within a single PGT laboratory cohort was 1.43%.

Result(s): All cell lines showed 100% concordance with the expected karyotype. Additionally, all evaluable rebiopsies showed 100% concordance with the original abnormal ploidy karyotype. The frequency of abnormal ploidy was 1.43%, with 29% of those being haploid or uniparental isodiploid, 2.5% uniparental heterodiploid, 68% triploid, and 0.4% tetraploid. Twelve haploid embryos contained maternal deoxyribonucleic acid, and 3 contained paternal deoxyribonucleic acid. Thirty-four triploid embryos were of maternal origin, and 2 were of paternal origin. Thirty-five triploid embryos had a meiotic origin of error, and 1 was of mitotic error. Of those 35 embryos, 5 originated from meiosis I, 22 originated from meiosis II, and 8 were deemed inconclusive. On the basis of specific abnormal ploidy karyotypes, 41.2% of embryos would be falsely classified as euploid, and 22.7% would be false-positive mosaics with the use of the conventional next-generation sequencing-based PGT methods.

Conclusion(s): This study demonstrates the validity of a high-throughput genome-wide single nucleotide polymorphism microarray-based PGT platform to accurately detect abnormal ploidy karyotypes and predict the parental and cell division origins of error of evaluable embryos. This unique method improves the sensitivity of detection for abnormal karyotypes, which can reduce the chances of adverse pregnancy outcomes.

Keywords: Abnormal ploidy; SNP array; embryo; preimplantation genetic testing.