PGTA (Preimplantation Genetic Testing for Aneuploidy) and PGTM (Preimplantation Genetic Testing for Monogenic Disorders) are both types of preimplantation genetic testing used in assisted reproductive technology (ART) to screen embryos for specific genetic abnormalities before they are transferred to the uterus during in vitro fertilization (IVF). Here's an overview of each type of testing and considerations for whether to pursue them:
PGTA (Preimplantation Genetic Testing for Aneuploidy):
PGTA is a type of genetic testing used to screen embryos for aneuploidy, which refers to an abnormal number of chromosomes. Aneuploidy can lead to chromosomal disorders such as Down syndrome (trisomy 21), Turner syndrome (monosomy X), and others.
Process:
Embryo Biopsy: A few cells are removed from each embryo on day 5 or 6 of development (blastocyst stage).
Genetic Analysis: The cells are analyzed to determine if the embryo has the correct number of chromosomes. This can take up to 2-4 weeks to complete.
Selection of Normal Embryos: Only embryos with the correct number of chromosomes are considered for transfer.
Considerations:
Advantages: PGTA can reduce the risk of miscarriage and chromosomal disorders by ensuring the embryo has the correct number of chromosomes.
Limitations: PGTA may not detect all genetic abnormalities, and false-positive or false-negative results can occur.
PGTM (Preimplantation Genetic Testing for Monogenic Disorders):
PGTM is a type of genetic testing used to screen embryos for specific monogenic disorders, which are caused by mutations in a single gene. This is often not necessary for recessive carrier genes, as you can select a donor that does not share the same carrier gene as the recipient parent. However, recipient parents may opt to do PGTM testing for dominant genes such as BRCA and Huntington's disease to ensure their child doesn't inherit these. For example, if the recipient parent has BRCA1 (a breast cancer predisposing gene) they can select for embryos that do not have this gene.
Process:
Embryo Biopsy: A few cells are removed from each embryo for genetic analysis.
Genetic Analysis: The cells are analyzed to determine if the embryo carries the genetic mutation(s) of concern.
Selection of Unaffected Embryos: Only embryos that do not carry the genetic mutation(s) are considered for transfer.
Considerations:
Advantages: PGTM can prevent the transmission of specific genetic disorders to offspring, allowing couples at risk of passing on genetic diseases to have healthy children.
Limitations: PGTM requires identification of the specific genetic mutation(s) of concern, and it may not be feasible for all genetic conditions. It also adds complexity and cost to the IVF process.
Should We Do It?
Whether to pursue PGTA or PGTM depends on various factors, including personal and medical considerations, genetic risk factors, and preferences. Here are some considerations to discuss with your healthcare provider:
Genetic Risk: If you or your partner have a known genetic disorder or are carriers of genetic mutations associated with an increased risk of genetic diseases, PGTM may be recommended to prevent the transmission of the disorder to your offspring.
Previous IVF Failures: If you have experienced multiple failed IUI/IVF cycles or recurrent miscarriages, PGTA may be recommended to screen for chromosomal abnormalities in embryos to reduce the risk of miscarriage.
Advanced Maternal Age: Women of advanced maternal age (typically over 35) have an increased risk of producing chromosomally abnormal embryos. PGTA may be recommended to screen embryos for aneuploidy.
Cost and Complexity: Both PGTA and PGTM add cost to the IVF process. Consider your financial situation, insurance coverage, and ideal time frame.
Ultimately, the decision to pursue PGTA or PGTM should be made in consultation with your healthcare provider, who can provide personalized guidance based on your specific circumstances, medical history, and reproductive goals.
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