Genetic testing explained
Regardless of whether conception occurred through ART or naturally, genetic testing is a process that can occur in any pregnancy. Also, note that women and couples can choose to undergo genetic testing before attempting to get pregnant. Different factors can be evaluated depending on the stage in which testing occurs. For example, some testing looks at the parents to see if either carries a gene for a genetic disorder. Other options screen the embryo for chromosomal abnormalities to determine the best candidate to transfer.
Testing the parents or donors
Genetic testing before conception is known as carrier screening. The evaluation focuses on the partners or donors to determine if either individual carries a gene for a concerning genetic condition. Some disorders can make conception more difficult, while others increase the likelihood of a baby being born with an inherited disability. Cystic fibrosis (CF), Tay-Sachs (TS), and sickle cell disease are just a few conditions that can be screened for with pre-conception carrier screening.
Testing after fertilization
For patients undergoing IVF, 2 different types of preimplantation genetic tests (PGT) exist for use after fertilization. Preimplantation genetic diagnosis (PGD) screens for specific hereditary disorders, while preimplantation genetic screening (PGS) looks for genetic abnormalities. Both tests occur before embryos are transferred to the womb.
PDG and PGS explained
Both PGD and PGS testing can be performed before the embryo transfer stage. Yet, the tests look at different issues. PGD is a good solution for a person who is a known carrier of a genetic disorder. With this test, technicians will only screen for the requested condition. By contrast, PGS is similar to prenatal genetic testing provided to pregnant women in the first trimester. Technicians will look for chromosomal abnormalities that suggest an embryo may be more likely to fail to implant into the uterine wall or result in miscarriage. If genetic abnormalities are present, the couple can decide to opt for donor eggs or sperm.
Regardless of the PGT screening selected, the testing is usually performed during assisted hatching. A technician will facilitate fertilization by cracking the egg’s shell to allow sperm to penetrate the egg. After fertilization, when the embryo becomes a blastocyst, technicians will biopsy cells from the exterior for genetic screening. Once results are available, the healthiest embryos are transferred to a woman’s uterus.
Who should be screened?
For patients with infertility, carrier screening can be a standard process before starting IVF. For PGD, the patient must be a carrier of a known genetic disorder. Additionally, individuals with a family history of genetic diseases are encouraged to choose PGD to learn more. PGS is recommended for women with recurrent miscarriages and individuals with multiple failed fertility treatments. PGS can also be chosen for personal reasons to avoid transferring an embryo at risk of a chromosomal abnormality.
Improving the odds
Genetic screening can provide more information so that a woman or couple can make a more informed decision. Remember that testing can’t guarantee conception or a healthy pregnancy. For more testing information, consider talking with a fertility specialist.