There are two main types of genetic testing that can be performed on embryos:
- Monogenic/Single Gene Disorder Preimplantation Genetic Testing (PGT-M)
PGT-M, also known as preimplantation genetic diagnosis (PGD), involves testing embryos for a specific known genetic mutation or disorder that runs in the family. This is done by removing one or more cells from the embryo via embryo biopsy and analyzing the DNA to determine which embryos are affected or unaffected by the genetic condition.
- Preimplantation Genetic Testing for Aneuploidy (PGT-A)
PGT-A, formerly known as preimplantation genetic screening (PGS), is a screening test to detect the most common chromosome abnormalities in embryos. The embryos are tested for conditions like Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), and Patau syndrome (trisomy 13). PGT-A can improve the chances of a successful pregnancy and reduce the risk of miscarriage for women of advanced maternal age or with a history of recurrent pregnancy loss.
Both PGT-M and PGT-A require in vitro fertilization (IVF) to produce embryos for testing. The embryos are tested at the blastocyst stage, around day 5 or 6 after fertilization. A few cells are removed from the trophectoderm, the outer layer of the blastocyst, for genetic analysis. The remaining cells in the embryo continue to develop normally. For uterine transfer, only unaffected embryos are chosen.
Genetic testing of embryos allows couples at high risk of passing on a genetic disease or chromosomal abnormality to have children who are genetically related but without the condition. However, there are risks to the IVF procedure and embryo biopsy, and not all embryos may be suitable or available for testing. You should discuss the options carefully with a fertility specialist to determine if genetic testing of embryos is right for your situation.