Genetics is the study of heredity and how qualities and characteristics are passed on from one generation to another.
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IVF With PGD (Preimplantation Genetic Diagnosis): Why is it needed?
Genetic screening technologies like PGD and PGS, when combined with IVF treatment, have made it possible to reduce the risk of passing on devastating genetic diseases, possibly reduce the risk of recurrent miscarriage, and possibly improve the odds of pregnancy success. As with all assisted reproductive technologies, it’s important you understand which situations the technology is best used for, the possible risks, the costs, and what to expect during treatment. You may see the acronyms PGD and PGS used interchangeably. They are both genetic screening technologies and both require IVF, but they are very different in why and how they are used. What Does PGD Mean? PGD stands for "preimplantation genetic diagnosis." The key word here is "diagnosis." PGS is used when a very specific (or set of specific) genetic disease needs to be identified in the embryo. This may be desired to avoid passing on a genetic disease or used to choose a very specific genetic tendency. Sometimes, both are needed—for example, when a couple wants to conceive a child who can be a match for a stem cell transplant for a sibling but also wants to avoid passing on the gene that causes the disease requiring a stem cell transplant. PGD does not test a single embryo for all possible genetic disease. This is important to understand. So, for example, if an embryo does not appear to have the gene for cystic fibrosis (CF), that doesn’t tell you anything about any other possible genetic disease that may be present. It only gives you the assurance that CF is highly unlikely. Possible Reasons for Testing for a Specific Genetic Diagnosis With IVF Here are possible reasons your doctor may recommend PGD (or reasons you may request it.) To avoid passing on a specific genetic disease that runs in the family: This is the most common reason for PGD. Depending on whether a genetic disease is autosomal dominant or recessive, the risk of passing on a genetic disorder to a child may be anywhere between 25 and 50 percent. In some cases, a couple may not otherwise need IVF to get pregnant, and may not be facing infertility. Their only reason for pursuing IVF may be for the PGD testing. As mentioned above, prenatal testing can also test for genetic diseases, without the added expense, risks, and costs of IVF treatment. But since the only option is pregnancy termination (or continuing the pregnancy) after prenatal testing, this is unacceptable to some couples. There are hundreds of genetic diseases that can be tested for, but some of the most common are: Cystic fibrosis Tay-Sachs Fragile-X Muscular dystrophy Sickle-cell anemia Hemophilia Spinal muscular atrophy (SMA) Fanconi's Anemia To screen for translocation or chromosomal rearrangements: Some people are born with all 46 chromosomes, but one or more are not in the expected position. These people may be otherwise healthy, but their risk of experiencing infertility, having a pregnancy result in miscarriage or stillbirth, or having a child with a chromosomal abnormality is higher than average. For couples that have a partner with a translocation, PGD can be used to help identify embryos more likely to be healthy. For human leukocyte antigen (HLA) matching, for stem-cell transplant: Stem-cell transplant is the only cure for certain blood diseases. Finding a match within the family is not always easy. However, PGD can be used to choose an embryo that both would be a stem-cell match (HLA match) and to possibly avoid passing on that same genetic disease affecting a sibling. If an embryo can be identified that is both an HLA match, and a pregnancy and healthy birth take place, the stem cells needed to save the life of the sibling can be collected from the umbilical cord blood at birth. To avoid passing on a genetic predisposition for an adult-onset disease: A slightly more controversial use of PGD is to avoid passing on genetic tendencies that may result in disease later in life. For example, the BRCA-1 breast cancer gene. Having this gene doesn’t mean a person will certainly develop breast cancer, but their risk is higher. PGD can be used to screen embryos for the BRCA-1 variant. Other examples include Huntington disease and early-onset Alzheimer disease. Content Source Featured Image Source