Preimplantation genetic testing (PGT) examines embryos during in vitro fertilization (IVF) before possible transfer to a woman’s uterus for a range of genetic problems that can cause implantation failure, miscarriage and birth defects in a resulting child.
These genetic defects include a missing or an extra chromosome in the embryo (for example, Down syndrome), single gene disorders (like sickle cell anemia), or the rearrangement of genes, which can cause pregnancy loss and birth defects.
We use three specific types of PGT (– PGT-A, PGT-M, PGT- SR), which is a new term encompassing the same functions as the previously named and more well-known preimplantation genetic diagnosis (PGD) and preimplantation genetic screening (PGS) embryo genetic tests.
Embryologists use PGT to find genetic defects in embryos during IVF, so those embryos will not be transferred to the woman’s uterus to achieve a pregnancy.
At MIRA Fertility, we conduct these PGT tests for two main reasons - One is to determine if embryos have genetic abnormalities that often cause failed implantation and miscarriage, resulting in unsuccessful IVF and the second is to identify embryos with genetic defects that can result in a child with a genetic disorder that could cause death or such inheritable conditions as muscular dystrophy.
Embryos found to have such flaws are excluded from being transferred to the mother’s womb for a pregnancy.
Preimplantation genetic testing refers to the three types of tests that may be performed on embryos during IVF:
Preimplantation genetic screening for abnormal chromosome number (PGT-A)
Preimplantation genetic testing for monogenic (individual) disease (PGT-M)
Preimplantation genetic testing structural rearrangement (PGT-SR) for known chromosomal mis-arrangements such as inversion and translocation.
Aneuploidy is one of the greatest causes of failed implantation for pregnancy and miscarriage, as well as a major cause of birth defects in children.
Candidates for PGT-A include:
Couples who have had a previous pregnancy with aneuploidy.
Women who have had two or more miscarriages.
Women who have experienced previous failed embryo implantation.
Women diagnosed with unexplained infertility.
Women older than age 35.
Women who have undergone numerous unsuccessful fertility treatments.
PGT-M analyzes for specific gene mutations that one (or both) of the parents is known to carry. A family background of genetic disorders in one or both parents can increase the possibility for a child to be born with a genetic mutation.
PGT-M examines common disorders including:
Sickle cell anemia.
BRCA1 & BRCA2 mutations.
PGT-SR analyzes embryos of patients known to have a chromosomal structural rearrangement, such as an inversion or translocation. Patients who have a known structural rearrangement are more at risk for producing embryos that do not have the correct amount of chromosomal material. The affected embryos are less likely to result in a live birth. Patients with these problems often have repeated miscarriages.
PGT-SR examines disorders including:
The final goal of any pre-implantation genetic testing is to improve the healthy pregnancy rate. However we should remember that it is not 100% accurate and the subsequent pregnancy should still be monitored like any pregnancy.
Reach us at Mira Fertility for more information. Contact Mira Fertility