Part of routine infertility testing involves preconception genetic screening, during which we take blood samples from the mother and see if any chromosomal or genetic abnormalities might block conception. Advanced technological innovations in fertility treatments allow us to test cellular tissue from blastocyst embryos (Day 5 after fertilization). The procedure is called preimplantation genetic testing (PGT).
Experienced embryologists remove several cells from the blastocyst(s) to perform preimplantation genetic testing. This process does not harm the embryos. Once the cells are safely removed, they are sent to a company specializing in genetic testing, and the embryos are frozen and safely stored for future IVF cycles..
These tests are not necessarily full-proof and can only show what is found in the very small cell sample provided. That said, they tend to be accurate, especially if testing reveals abnormalities. Once the results are back, patients use the information to determine what comes next, which might include:
- Moving forward with IVF using embryos free from the most common chromosomal or genetic abnormalities.
- Considering the use of donor eggs, donor sperm, or donor embryos.
- Making decisions about what to do with unused embryos.
The information we learn from PGT both informs and optimizes fertility treatments and may also increase your chances of fertility success. There is more than one type of PGT, the results of which help us to create a clearer assessment of what may or may not be causing early or recurrent miscarriages, as well as failed fertility treatments.
There are three different types of PGT:
Preimplantation genetic testing for aneuploidy (PGT-A) examines the number of chromosomes in an embryo. The use of PGT-A has increased dramatically over the past several years. It is most beneficial to women who are 36 years old and older because egg quality diminishes rapidly as women approach and pass the 40-year mark. Healthy humans have 23 pairs of chromosomes, meaning 46 chromosomes altogether. Missing or extra chromosomes increases your risks of failed implantation and miscarriage. In addition, if the pregnancy continues, the baby will be born with a chromosomal defect, such as Down’s Syndrome or Turner Syndrome.
During testing, genetic lab technicians look for euploid embryos, which means there is a normal number of chromosomes.
Preimplantation genetic testing for structural rearrangements (PGT-SR) looks at how the chromosomes are arranged. Remember we mentioned infertility testing includes preconception genetic screening. Sometimes, parents are carriers of a defect they don’t have. In some cases, for example, the mother or father may have structural rearrangements of the chromosomes. These might not affect your physical appearance, health, or wellbeing, but those rearrangements can cause problems with your offspring.
This might mean portions of the chromosomes are translocated (moved from one part of a chromosome to another) or inverted (a portion flipped upside down and reattached). If testing reveals structural rearrangements, you have a higher chance of miscarriage or having a baby with genetic disorders.
Preimplantation genetic testing for monogenic/single gene defects (PGT-M). Geneticists suggest there are upwards of 10,000 different monogenic or sing gene defects. While there is no way to test for all of them, we do have the ability to test for some of the most common, including:
- Cystic fibrosis
- Sickle cell anemia
- Tay Sachs
- Duchenne muscular dystrophy
- Specific cancers (including BRCA – breast cancer)
This helps couples to make more informed chances when selecting which embryos to transfer, avoiding any that test positive for specific disorders or mutations.
We do not doubt that preimplantation genetic testing reduces a woman’s chances of giving birth to a baby with a genetic or chromosomal disorder/defect. Studies also indicate they benefit women who are 36 years old and older. Whether or not these tests improve fertility chances for younger women is a lively topic of debate in the fertility treatment arena, and research is ongoing.
Are you interested in learning more about whether you’re an ideal candidate for these different types of PGT? Then, schedule a consultation with Fertility Solutions. We are proud to provide comprehensive advice, treatments, and specialized testing to improve all patients’ chances of fertility treatment success.