This advanced laboratory procedure screens embryos for genetic diseases or chromosomal abnormalities prior to placing them in the uterus.
Couples utilizing preimplantation genetic diagnosis have their embryos evaluated prior to transfer and only the most genetically normal embryo(s) are selected. It is a relatively complex procedure that involves manipulation of the embryo, so it is offered judiciously to patients in situations where the benefits outweigh the risks.
Introduced in the 1990s, PGD’s purpose was to help patients avoid passing genetic diseases, such as cystic fibrosis or Tay-Sachs, to their child. It has been shown to be very effective for this purpose, and its indications have now expanded. For example, PGD is used as a screening test for aneuploidy, which is an error in cell division resulting in an embryo with either too many or too few chromosomes. Chromosomal abnormalities are the most common cause of miscarriage and are often a reflection of reproductive aging (otherwise known as the female “biological clock”).
Pre-Implantation Genetic Screening: PGS
PGD is also used as a tool to prescreen embryos for chromosomal abnormalities (preimplantation genetics screening – PGS) in patients over the age of 35 to help the embryologist and physician choose the best embryo(s) to transplant into the uterus. Utilizing PGD in this context can be controversial and should only be performed after extensive counseling.
Patients who believe they are candidates for PGD should schedule a separate consultation with their fertility specialist. At that consultation, detailed information (including risks and benefits) will be reviewed and their treatment strategy will be individualized based on their situation.
Since this procedure involves an embryo biopsy, which is equivalent to surgery on the embryo on a microscopic level, there is approximately a one to three percent chance that the embryo will be harmed. Having an experienced embryologist perform the biopsy minimizes this risk.
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