Noninvasive preimplantation genetic testing for aneuploidy in spent medium may be more reliable than trophectoderm biopsy.

Preimplantation genetic testing for aneuploidy (PGT-A) with trophectoderm (TE) biopsy is widely applied in in vitro fertilization (IVF) to identify aneuploid embryos. However, potential safety concerns regarding biopsy and restrictions to only those embryos suitable for biopsy pose limitations. In addition, embryo mosaicism gives rise to false positives and false negatives in PGT-A because the inner cell mass (ICM) cells, which give rise to the fetus, are not tested. Here, we report a critical examination of the efficacy of noninvasive preimplantation genetic testing for aneuploidy (niPGT-A) in the spent culture media of human blastocysts by analyzing the cell-free DNA, which reflects ploidy of both the TE and ICM. Fifty-two frozen donated blastocysts with TE biopsy results were thawed; each of their spent culture medium was collected after 24-h culture and analyzed by next-generation sequencing (NGS). niPGT-A and TE-biopsy PGT-A results were compared with the sequencing results of the corresponding embryos, which were taken as true results for aneuploidy reporting. With removal of all corona-cumulus cells, the false-negative rate (FNR) for niPGT-A was found to be zero. By applying an appropriate threshold for mosaicism, both the positive predictive value (PPV) and specificity for niPGT-A were much higher than TE-biopsy PGT-A. Furthermore, the concordance rates for both embryo ploidy and chromosome copy numbers were higher for niPGT-A than TE-biopsy PGT-A. These results suggest that niPGT-A is less prone to errors associated with embryo mosaicism and is more reliable than TE-biopsy PGT-A.

Randomized controlled trial of low (5%) versus ultralow (2%) oxygen for extended culture using bipronucleate and tripronucleate human preimplantation embryos.

OBJECTIVE: To determine whether [1] exposure of embryos to 5% oxygen (O2) from day 1 (D1) to D3, and then to 2% O2 from D3 to D5, improves total blastocyst yield, as compared with continuous exposure to 5% O2; and [2] extended culture in 2% O2 alters key metabolic processes and O2-regulated gene expression in human preimplantation embryos. DESIGN: Randomized controlled trial. SETTING: Academic medical center. PATIENT(S): Bipronucleate and tripronucleate embryos donated for research. INTERVENTION(S): On D1, sibling zygotes were randomized to culture in 5% O2 from D1 to D5 (n = 102; "5% group") or 5% O2 from D1 to D3, then 2% O2 from D3 to D5 (n = 101, "2% group"). MAIN OUTCOME MEASURE(S): Developmental stage and grade; D5 total cell counts; mass spectrometry of spent media; quantitative polymerase chain reaction of 21 genes in inner cell mass and trophectoderm. RESULT(S): Among cleaved embryos (n = 176, 87%), those in the 2% group were less likely to arrest at the cleavage stage on D5 (34 of 87, 39.1%) compared with the 5% group (52 of 89, 58.4%) (adjusted odds ratio 0.38, 95% confidence interval 0.18-0.80). Those in the 2% group were more likely to blastulate (35 of 87, 40.2%) than those in the 5% group (20 of 89, 22.5%) (adjusted odds ratio 2.55, 95% confidence interval 1.27-5.12). Culture in 2% O2 was associated with significantly fewer cells in early and advanced blastocysts, alteration in relative abundances of anabolic amino acids and metabolites involved in redox homeostasis, and differential expression of MUC1 in trophectoderm. CONCLUSION(S): These findings provide foundational evidence for future investigation of 2% O2 as the preferred O2 tension for extended culture of human embryos.