From the Guidelines
Embryo grading and genetic testing are distinct methods for evaluating embryos during IVF, with embryo grading assessing visual appearance and development, and genetic testing analyzing chromosomal makeup. The grading system, such as 4AA, 3AB, 3BB, 4BB, 4BC, evaluates the expansion stage and quality of inner cell mass and trophectoderm cells, with 4AA being the highest quality among those listed 1. Genetic testing, including PGT-A, detects chromosomal abnormalities, and an embryo with excellent visual grading can still have genetic abnormalities, while lower-graded embryos might be genetically normal 1. Key points to consider for polygenic risk scores in embryo selection include the clinical context, risk vs benefit, and the need for pre- and post-test counseling with a detailed discussion of probabilistic information and risk reductions 1. The clinical utility of polygenic risk scores for embryo selection has not yet been shown, and medical professionals should make this clear to individuals requesting PGT-P, with a discussion of potential harm in some clinical situations 1. Both evaluation methods provide complementary information, and using both gives a comprehensive assessment for selecting embryos with the highest potential for successful pregnancy. Some key considerations for PGT-P include:
- The clinical context in which individuals pursue PGT-P affects the choices they have in terms of the number and types of embryos 1
- The decision process is complex and may require trade-offs if PGT-P is done for multiple conditions at once 1
- Medical professionals should refuse to facilitate PGT-P if the risks outweigh the benefits, such as when IVF is being done solely for the purpose of PGT-P 1. In terms of counseling, it is essential to have a detailed discussion of how to interpret probabilistic information, as well as both relative and absolute risk reductions generated by PRS, with a clearly written report and visual aids 1. Counseling is best done in an individualized objective approach by a non-partisan board-certified genetics health care professional 1. Overall, embryo grading and genetic testing are two different methods that provide complementary information, and using both is essential for selecting embryos with the highest potential for successful pregnancy.
From the Research
Embryo Grading and Genetic Testing
- Embryo grading, such as 4AA vs. 3AB, 3BB, 4BB, 4BC, is a method used to evaluate the quality of embryos in in vitro fertilization (IVF) cycles.
- Genetic testing, including preimplantation genetic testing for aneuploidy (PGT-A), is used to detect genetic abnormalities in embryos.
- The provided studies do not directly compare embryo grading with genetic testing, but they do discuss the use of genetic testing in IVF cycles and the potential for transferring embryos with genetic anomalies.
Genetic Testing and Embryo Transfer
- A study published in 2017 2 discusses the ethics of transferring embryos with genetic anomalies detected in preimplantation testing.
- Another study published in 2022 3 reports on the outcomes of transferring embryos with abnormal PGT-A biopsies and found that such transfers can result in live births.
- A 2009 study 4 provides an overview of preimplantation genetic diagnosis (PGD) and its applications, including the selection of embryos for transfer based on genetic analysis.
Preimplantation Genetic Testing
- A 2021 study 5 discusses the use of preimplantation genetic testing (PGT) for X-autosome translocation carriers and reports on the successful transfer of non-carrier embryos.
- A 2017 study 6 reports on the use of improved genetic technologies for PGT-A and the potential for rescuing viable embryos from abnormally fertilized oocytes.
Differences between Embryo Grading and Genetic Testing
- Embryo grading is a morphological evaluation of embryo quality, while genetic testing is a molecular analysis of embryo genetics.
- Genetic testing can detect genetic abnormalities that may not be apparent through embryo grading alone.
- The provided studies suggest that genetic testing can be a valuable tool in selecting embryos for transfer, but they do not directly compare the effectiveness of embryo grading versus genetic testing.