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What is PGT-A & Who Should Consider It?
October 14, 2024Labryo Fertility Center
EducationalAssisted reproductive technology (ART), such as in vitro fertilization (IVF), has helped many individuals and families lighten the burden of infertility. However, even with IVF, the risk of miscarriages or the birth of a child with genetic abnormalities remains. Thus, genetic testing can be crucial in increasing the chances of a successful pregnancy with a healthy baby.
One of the most common types of preimplantation genetic testing (PGT) used during IVF treatment is PGT-A testing. This article will delve into the details of this genetic screening procedure, explaining what PGT-A tests for, who should consider it, the steps involved, and the potential benefits, helping patients make informed decisions during their fertility treatment.
1. What is PGT-A Testing?
Preimplantation genetic testing for aneuploidy (PGT-A) was previously known as preimplantation genetic screening (PGS). It is a screening procedure that evaluates the number of chromosomes in embryos within the limits of test resolution.
Chromosomes are the structures that contain genetic material within our cells and a healthy human embryo should have 46 chromosomes, 23 from the egg and 23 from the sperm. In contrast, an embryo with aneuploidy may have an extra or missing chromosome. With PGT-A, the doctors can help determine if an embryo is euploid (meaning it has all chromosome pairs) or aneuploid (meaning the embryo may have extra or missing chromosomes).
According to research by the American Society of Human Genetics, aneuploid embryos have up to 86.3% risk of miscarriage as they usually experience difficulty implanting in the uterus. Even if the embryos are implanted successfully, aneuploid embryos may still have difficulty in developing. This can lead to genetic disorders (e.g. Down syndrome, Turner syndrome, and Klinefelter syndrome) within the future child.
2. How Does PGT-A Testing Help with Pregnancies?
A study in Reproductive Biomedicine shows that PGT-A-tested embryo transfers resulted in higher live birth rates than non-PGT-A transfers, both for fresh (49.5% vs. 38.6%) and frozen embryos (50.6% vs. 35.8%). This contrast is particularly prevalent when patients have a higher maternal age, as seen in the graph below:
Although PGT-A does not directly alter an embryo's chromosomes or screen for specific genetic conditions, it can help choose the most viable embryo for transfer during infertility treatments. Not only can this minimize the risk of miscarriages and congenital conditions at birth, but it can also reduce the risk of multiple gestational pregnancies per IVF cycle, thus increasing the likelihood of a safe and healthy pregnancy.
3. What is the Difference between PGT-A, PGT-SR, and PGT-M?
These three procedures assess embryos for different genetic conditions. Unlike PGT-A, PGT-SR (preimplantation genetic testing for structural rearrangements) tests for structural abnormalities in chromosomes, such as translocations or inversions, which can increase the risk of chromosomal imbalances in embryos. On the other hand, PGT-M (preimplantation genetic testing for monogenic disorders) tests for specific single-gene disorders, such as cystic fibrosis or sickle cell anemia.
| Test Type | PGT-A | PGT-SR | PGT-M |
|---|---|---|---|
| Screening Factor | Extra or missing number of chromosomes | Chromosomal rearrangements | Specific single-gene conditions |
| Purpose | Prevent miscarriages or congenital issues related to aneuploidy | Prevent miscarriages related to translocations or inversions | Prevent X-linked, autosomal recessive, and autosomal dominant diseases |
| Recommended For | All IVF patients, especially women in a higher age group | Patients who are carriers of chromosomal imbalance | Patients with a history of genetic disorders or those who are recessive carriers |
4. Who Should Consider PGT-A?
PGT-A testing is available for most females undergoing IVF and it is often recommended for patients who:
- Are over 35 years old
- Have a history of miscarriages
- Experienced multiple failed IVF treatments
- Had a child with a genetic or chromosomal condition
- Have a family history of chromosomal issues
This is because chromosomal abnormalities occur by accident during the formation of eggs or sperm (meiosis) or in the early stages of fetal development (mitosis), and research by the National Human Genome Research Institute suggests that the maternal age and environmental factors could potentially increase the risk of such conditions. Hence, patients should consult their fertility specialist to decide whether or not they should use PGT-A based on their personal circumstances.
5. How Does PGT-A Work: The 6-Step Process
If you're considering PGT-A, it's essential to discuss your options with your fertility specialist early on. The entire process could take 2 to 6 weeks so it must be planned ahead to be integrated into the IVF treatment plan. Here are the steps involved:
Step 1. In Vitro Fertilization (IVF)
Patients will undergo hormone stimulation with medication to produce multiple eggs. These eggs are then retrieved and fertilized with sperm to create an embryo within the clinic’s laboratory.
Step 2. Embryo Biopsy
Once the embryos reach the blastocyst stage after 5 to 6 days, a few cells will be collected as samples. At this stage, each embryo consists of 50-150 cells, some of which will develop into the fetus and others into the placenta. Only cells from the outer layer, the ones that will become the placenta, will be biopsied for PGT-A testing as this minimizes the risk of harming the embryo.
Step 3. Shipment
The embryos will then be frozen immediately after biopsy and stored at the fertility clinic, while the biopsied cell samples are sent to a specialized genetic laboratory for analysis.
Step 4. Genetic Analysis
With advanced equipment, the genetic laboratory will examine all the embryos' chromosomes to determine if there are any abnormalities.
Step 5. Results Review
After 1 to 2 weeks, the PGT-A results will be sent back and reviewed by the patient’s fertility specialist. The patient will receive a detailed report that outlines the chromosomal status of each embryo, showing whether they have euploidy (the correct number of chromosomes) or aneuploidy (the incorrect number of chromosomes).
Step 6. Embryo Transfer
Using the PGT-A results, IVF patients can select the suitable embryo(s) for transfer. The doctor will prescribe medication to thicken the patient’s uterine lining and transfer the thawed embryo after 2 to 3 weeks.
6. Frequently Asked Questions About PGT-A Testing
6.1. Does PGT-A have any risks?
PGT-A itself does not pose additional risks to the IVF patient. Nonetheless, there are potential risks associated with the biopsy and testing that may affect the embryos:
- Inaccurate Results: While PGT-A is highly accurate, as with any test, there is a chance for errors. Examples include but are not limited to false positives indicating an abnormality that isn't present or false negatives that miss an existing abnormality.
- Potential Damage to the Embryo: The biopsy process involved in PGT-A can carry a small risk of damaging the embryo and stunting its development, but this can be prevented by choosing an IVF lab with experienced and skilled embryologists.
- Embryo Discards: If the embryos tested are aneuploid, they may be discarded, This reduces the amount of embryo available for transfer. In the instance that all embryos are discarded, patients will have to go through another retrieval cycle.
If an IVF patient isn’t sure about the potential risks of PGT-A, it is recommended to discuss it with their fertility specialist. The doctors will provide personalized guidance based on each patient’s individual circumstances.
6.2. How much does PGT-A cost? Is it covered by insurance?
The average cost of PGT-A ranges from $4,000 to $10,000. This is influenced by several factors, including the number of embryos tested, the location of the fertility clinic, insurance coverage, etc.
Some insurance plans may partially or fully cover PGT-A, while others may not, so patients will have to check with their insurance provider to determine the specific coverage. Even if the insurance doesn't cover PGT-A, several fertility clinics offer financing options to make the procedure more affordable.
6.3. Can PGT-A be done if the sperm or eggs are from anonymous donors?
Typically, PGT-A can be performed without additional DNA samples from the sperm or egg donor. The genetic analysis is based on the DNA extracted from the embryos themselves. However, for PGT-M, additional DNA samples may be required so it's best to consult with a fertility specialist to determine the specific requirements.
6.4. Can PGT-A be used to screen gender?
Yes, PGT-A can be used for gender selection. While its primary purpose is to screen for chromosomal abnormalities, the same process can also identify the embryo’s sex. This information can be used to avoid gender-linked genetic disorders. But, it's crucial to note that gender selection using PGT-A may not be readily available in all regions. It is also important for you to know that PGT-A testing can be done where gender is masked if one does not want to know the gender beforehand.
7. Comprehensive PGT-A Testing at Labryo Fertility Center
An experienced IVF clinic will work with a PGT-A testing laboratory to provide accurate screening results, which can help increase the chances of a healthy pregnancy.
Labryo Fertility Center is a trusted destination for PGT-A testing and IVF treatments. Leveraging the latest advancements in reproductive medicine, our expert team is committed to providing top-tier personalized care throughout your fertility journey.
We offer a wide range of fertility services, including IVF, PGT-A, and other diagnostic procedures, helping you receive all the necessary support in one convenient location. Contact Labryo Fertility Center and schedule a consultation with us today.