Everything You Need to Know About Genetic Carrier Screening and PGT

When you start fertility treatment, so many tests are recommended and it’s hard to know what they’re for and which tests apply to you. Genetic testing is becoming more and more prevalent. We’ve answered some of the top questions about genetic testing to help you decide if it’s right for you.

What is genetic carrier screening?

Genetic carrier screening is a blood test that’s used to detect recessive genetic conditions. A recessive genetic condition is a disorder that requires one copy of the gene from each parent for the condition to appear in a child. The testing requires a simple blood draw and can often be completed right at your fertility clinic. The blood samples are sent off to a lab that analyzes your chromosomes for genes that indicate certain conditions.

The results of the testing take a week or two to get back. Once you receive your results, you can discuss them with your doctor or your clinic’s genetic counselor to determine if any follow-up is needed.

Who should do genetic carrier screening?

Anyone can do genetic carrier screening, but the test is aimed mostly at people who are looking to start a family. For those looking to start a family, both genetic parents should do carrier screening to confirm that they do not carry the same recessive conditions. 

Genetic carrier screening is also important for people who know that they have disorders in their family that are passed down through genetics, like sickle cell anemia, cystic fibrosis, or Tay-Sachs disease. If close relatives are known to have or to carry a genetic disorder, it’s a good idea to have yourself tested to understand if you also carry a gene for the condition. 

What happens if I'm found to be a carrier?

If you are found to be a carrier of a condition, the first step is to look into the condition and to see if the same condition is carried by your partner. If not, the next step is to let your family know that this condition runs in your family. Because you carry this recessive gene, it’s likely other members of your family will too. So, it can be helpful to let them know in case they want to do screening as well. 

What happens if my partner or spouse is found to be a carrier of the same condition as I am?

If both partners carry the same condition, there is a 25 percent chance that your child will inherit both copies of the gene and have the disease. The next step is to speak with a genetic counselor to make sure that you are well informed about what the condition is and what it would mean for your future children. There are a few options for moving forward:

• Try to conceive naturally or through non-selective measures like Intrauterine Insemination (IUI) and risk passing the condition on to your child.

• Proceed with IVF and test the embryos for the condition through a test known as PGT-M (discussed in detail below). Then choose to transfer an embryo that is not affected by the condition.

Speaking with your doctor and the genetic counselor is the best way to fully grasp the symptoms of the condition and to know which next step is best for planning your family.

How can I use genetic testing results in family planning decisions?

Many couples choose to genetically test their embryos following an IVF cycle through a process known as PGT (Preimplantation Genetic Testing). As the embryos are cultured in the lab after the IVF cycle, they will grow to reach a stage of development known as a Blastocyst. The blastocyst stage is when the Embryologist will remove a few cells from the outer portion of the embryo and send them off for PGT. 

There are three different types of preimplantation genetic testing, PGT-A, PGT-M, and PGT-SR.

PGT-A

PGT-A (preimplantation genetic testing for aneuploidy) is a test that checks the cells from each embryo to confirm that they have the correct number of chromosomes. An embryo that has 46 chromosomes is considered normal or Euploid . An embryo that has too few or too many chromosomes is abnormal or Aneuploid. 

Anyone can do PGT-A, but it’s most often recommended for patients who’ve had recurrent miscarriages and for patients older than 35, who are at higher risk for lower egg quality resulting in more aneuploid embryos. Transferring an embryo that has been confirmed to be normal results in higher pregnancy rates. 

PGT-M

PGT-M (preimplantation genetic testing for a Monogenetic disorder) is a test that checks the embryos for a specific genetic condition. This testing is recommended when both parents test positive for the same condition, like cystic fibrosis or muscular dystrophy for example. The cells of the embryos are sent off for testing and the results will come back and show which embryos are affected by the genetic disorder and which aren’t. This allows you to select an embryo that is unaffected by the disorder and transfer it into the uterus to create a pregnancy and, therefore, avoid passing on the condition to a child.  

The intended use of PGT-M can delay starting an IVF treatment cycle. This is because the lab has to create something called a probe, which allows their testing equipment to be able to search for and find the specific disease-carrying gene in the embryos. This process can take time and the PGT-M can’t happen without it. 

PGT-SR

PGT-SR is another form of specific genetic testing for structural genetic problems passed down from the parents. These hereditary structural issues often result in miscarriages. PGT-SR is used to identify these structural rearrangements within the tested embryos. Similar to PGT-M, the test results allow you to choose an unaffected embryo for transfer, which leads to higher chances of creating a successful pregnancy. 

Cost of Genetic Testing

Genetic Carrier Screening

Genetic carrier screening blood draw and analysis tends to be relatively inexpensive. The testing typically costs a few hundred dollars and is often covered fully or partially by standard health insurance plans. The exact amount varies depending on your insurance coverage, your clinic, and what lab company is completing the test. 

PGT Testing

PGT testing can accrue a larger cost. According to FertilityIQ, PGT-A costs on average about $5,000 per IVF cycle. 

PGT-M and PGT-SR can be more expensive processes than PGT-A due to their personalized nature. The cost can vary per case and per lab. If PGT-M or PGT-SR may be part of your treatment plan, be sure to speak with your clinic and preferred lab in regards to the cost for your specific case.

Genetic testing is a very useful tool in terms of determining who is a carrier of certain recessive conditions and choosing the best embryo to transfer to have the best chances at creating a successful pregnancy. Knowing the basics about genetic testing and what your options are can help you make the most educated decisions as you navigate your fertility journey.