Abstract
Study question
Can non-invasive preimplantation genetic testing of aneuploidies (niPGT-A) improve the clinical outcome in IVF patients after proper validation?
Summary answer
We demonstrate the usefulness of the embryonic cell-free DNA (cfDNA) in the blastocyst culture medium to select more objectively the blastocysts with higher implantation potential.
What is known already
One of the greatest challenges in IVF is accurately selecting viable embryos that are more likely to achieve healthy livebirths following embryo transfer. Trophectoderm (TE) biopsy and PGT-A provide a direct assessment of chromosome status and improve implantation and clinical pregnancy rates per transfer. A non-invasive alternative is to analyse embryonic cfDNA in the blastocyst culture medium. Previous studies have shown that cfDNA testing in culture medium of blastocysts on day 6 of development allows aneuploidy detection with high concordance rates compared to TE biopsy and inner cell mass (Rubio et al., 2020).
Study design, size, duration
Observational study of the clinical application of niPGT-A (July 2020-December 2020). The clinical application consisted in a first validation phase, comparing TE biopsies with cfDNA in the media of 28 blastocysts. And, in a second phase, niPGT-A was applied and the outcome of 13 single embryo transfers (SETs) compared to 13 PGT-A SETs and 130 IVF/ICSI SETs performed in a period of six months. In the three groups, women and donors age was ≤38 years.
Participants/materials, setting, methods
Embryos were cultured in a Geri incubator (Merck) up to day 4, and then individually cultured in 10µl drops of CCSS (Fujifilm) until day 6 in a bench-top K-system. At day 6, blastocysts were vitrified, and media collected in sterile PCR tubes after at least 40 hours in culture. After collection, media were immediately frozen and analyzed by NGS analysis in our reference laboratory (Igenomix, Spain). Deferred transfer was performed according to media results.
Main results and the role of chance
Before the first clinical cases, a validation of the protocol comparing the results of cfDNA with the TE biopsies of the same day–6 blastocyst was performed, and ploidy concordance rates were 87.5%.
Similar results were found for niPGT-A and PGT-A in terms of aneuploidy results and in clinical outcomes. The percentages of informative results were 95% and 97% and the aneuploidy rates were 44% and 46%, for niPGT-A and PGT-A, respectively. Clinical pregnancy rates were in both groups of aneuploidy testing, 69.2%, with 8 ongoing pregnancies (61.5%) and 4 tested by prenatal screaning NACE. For untested embryos clinical pregnancy (57.7%) and ongoing pregnancy rates (48.5%) were lower than in the two groups of tested embryos (niPGT-A and PGT-A).
In the niPGT-A cycles embryo transfer was performed according to media results and morphology. We did a secondary analysis of which blastocyst we would transfer, if only morphology is considered. We observed that if we only select the embryos by morphology, in 61.5% of the cases we would choose the same embryo than with niPGT-A, and in 30.4% of the cases we would transfer a blastocyst with an aneuploid medium.
Limitations, reasons for caution
Our results are encouraging but should be interpreted with caution due to the small sample size. Larger and randomized controlled trials are needed to verify and extend our findings in each group.
Wider implications of the findings: We observed consistent results for niPGT-A compared to TE biopsies in our internal validation. These results endorse the clinical application of niPGT-A in the routine of the laboratory and can avoid the embryo manipulation also reducing the subjectivity when embryos are selected only by morphology.
Trial registration number
Sa–16552/19-EC:428
High efficacy of non-invasive chromosome screening using spent culture medium for preimplantation genetic testing of human embryos
