PGT-A (previously known as preimplantation genetic screening or PGS) involves checking a few cells of the embryos for potential abnormalities in the number of chromosomes. Embryos with an abnormal number of chromosomes in all or in the majority of their cells (known as aneuploid embryos) may have lower chance of developing into a baby or, less commonly, may result in a baby being born with a genetic condition. In order to obtain embryonic genetic material for analysis, a biopsy procedure is required, involving the removal of several cells. This invasive procedure greatly increases the costs of PGT and there have been concerns that embryo viability could be compromised due to the invasive technique. The recent discovery of intact embryonic DNA in spent embryo culture media (SCM) has led to interest in the development of non-invasive methods of PGT (niPGT).
Available data suggest that SCM samples frequently provide DNA templates suitable for genetic analyses, offering potential means of PGT that is less expensive than traditional methods, requires less micromanipulation and poses no risk to embryos. Dr Christine S. Allen et al., designed a study to compare KPI results of non-invasive Pre-Implantation Genetic Analysis (PGTA) testing commercially available for clinical use to those of traditional biopsied samples PGTA in assisted reproductive technology (ART).
A controlled, direct comparison retrospective analysis was performed, randomized by age and patient diagnosis, incubator type, performing MD, and culture medium type. Patients undergoing IVF treatment including PGTA at one single IVF laboratory, during the year of 2021 were included.
The results showed that for the non-invasive PGTA cases group:
- 73% of transfers tested positive for beta human chorionic gonadotropin (beta hCG) (N=11)
- 77% implantation rate (N=13)
- 45% of transfers had a clinical pregnancy confirmed by presence of intra uterine gestational sac and fetal heart beat
- After a maximum of 2 transfers within one year post- egg retrieval, 72% of non-invasive PGTA cases had a healthy delivery, with one case of twins(N=7).
The control group showed:
- 64% positive beta hCG per transfer (N=11)
- 29% implantation rate per transfer (N=14)
- 36% clinical pregnancy rate per transfer confirmed by presence of intra uterine
gestational sac and fetal heart beat
- 38% of patients had a healthy delivery per egg retrieval after one year post egg retrieval procedure.
No delivery complications, low birth weight (LBW) or abnormalities were present in any of the born babies, in any of the two groups.
No errors in euploidy or gender were observed on the non-invasive PGTA group, however, a normal baby pregnancy was achieved from a deemed aneuploid biopsied embryo. Results
were not statistically significant for any of the above parameters, according to paired
T-test analysis, due to low power ( low N).
These preliminary results suggest that non-invasive PGTA testing may offer an improved technology alternative and may offer benefits over traditional biopsy samples in ART. However, it is important to note that these results were based on a low sample size (N) and had low statistical power. Further studies with larger sample sizes and stronger statistical power are necessary to confirm these findings and fully understand the benefits of non-invasive PGTA testing.
In conclusion, this study found that the non-invasive PGTA test showed an overall higher success rate compared to the randomized by age and patient diagnosis control group subjected to conventional biopsy PGTA. The use of non-invasive PGTA testing in ART shows promise, but further research is needed to confirm these preliminary results and determine the full benefits of this technology.
This article is based upon research published by FC Consulting Partner Dr. Christine Allen and authored by FC Consulting Partner Alice Davenport, who has experiences among other areas from working with services and products within the field of genetic testing.
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