Description
Genetic screening plays a crucial role in the process of embryo selection for in vitro fertilization (IVF) by identifying potential genetic disorders in embryos before implantation. This screening, often referred to as preimplantation genetic testing (PGT), involves analyzing embryos for chromosomal abnormalities or specific genetic mutations. It helps in selecting the healthiest embryos, reducing the risk of passing on inherited conditions, and increasing the chances of a successful pregnancy. PGT can identify conditions such as Down syndrome, cystic fibrosis, and certain inherited cancers, allowing parents to make informed decisions about which embryos to implant. This technology enhances the overall outcome of IVF by improving the quality of embryos and reducing the likelihood of miscarriage. Ultimately, genetic screening offers a valuable tool for optimizing reproductive success and promoting healthier pregnancies.
Summary Listen
- Genetic testing, specifically preimplantation genetic testing (PGT), is used to diagnose embryos before implantation to avoid transferring embryos with DNA damage. It began focusing on inherited disorders but has expanded to encompass genetic screening for chromosomal abnormalities, potentially improving IVF outcomes. Selecting the best embryo involves multiple factors, including morphological assessment, cell symmetry, fragmentation, cell division, kinetics, blastocyst development, and time-lapse imaging, to maximize pregnancy success and minimize multiple pregnancies.
- Embryo viability tests and embryo transfer timing are important considerations, as is careful preservation and thawing techniques. Patient-specific factors like infertility causes, maternal age, hormonal levels, and uterine environment must also be considered. Artificial intelligence and standardized embryo assessment protocols are increasingly used in embryo selection.
- Chromosomal abnormalities include numeric abnormalities, structural abnormalities, and mosaicism. Aneuploidy is present in a significant percentage of human embryos, with higher rates in older mothers. Mosaicism, where cells have different chromosome compositions, presents unique challenges for embryo selection.
- PGT techniques have evolved from sex determination using PCR to FISH for detecting chromosomal abnormalities, initially on cleavage-stage embryos (day 3) and more recently on blastocyst-stage embryos (day 5). Blastocyst biopsy provides more comprehensive information by differentiating between cells that will form the fetus and the placenta. PGT is now used in cases of repeated implantation failure, pregnancy loss, previous trisomic conceptions, male factor infertility, and with egg donors, particularly in advanced maternal age. Understanding the maternal or paternal contribution to aneuploidy is valuable for guiding gamete donation decisions.
- Embryos possess self-correction mechanisms that eliminate abnormal cells, but challenges in PGT exist due to patient factors, procedural risks, technical limitations, and strategy selection. Variation in aneuploidy rates and miscarriage rates after PGT across different centers highlights the importance of expertise and technique. PGT utilization rates vary significantly among clinics based on patient population and physician philosophies. The cost-effectiveness of PGT must also be considered, as it can add significantly to the overall cost of IVF treatment.
- The quality of the biopsy, the number of cells removed, and the blastocyst quality all impact pregnancy rates after PGT. Artifactivity in results and the lack of benefit in young patients are important considerations. Emerging technologies in PGT include comparative genomic hybridization, array comparative genomic hybridization, single nucleotide polymorphism microarrays, and next-generation sequencing, each with its own limitations.
- Transcritomic pre-implantation genetic testing, linking PGTA with embryo competence and transcritomics, shows promise but requires further research. Ethical and economic considerations surrounding PGT include the moral status of the embryo, the economic impact of the procedure, and the need for quality control and regulation in PGT labs. The emotional burden on patients should also be acknowledged. Newer tests detect novel mutations that may impact embryo survival.
- In conclusion, while PGT may provide valuable information on embryo quality, its routine use remains controversial. Enhanced embryoculture practices and advanced genetic testing methods are needed to improve outcomes.
Sample Certificate
About the Speakers
Dr. Yolanda Cabello,
Senior Clinical Embryologist, VIU, Madrid, Spain
Comments
Comments
You must be logged in to leave a comment.