If you are going through IVF, your doctor may have mentioned PGT-A, preimplantation genetic testing for aneuploidy, as an optional addition to your cycle. Perhaps you have heard other patients in online communities swear by it, or perhaps you have read conflicting opinions about whether it is truly worth the added cost and complexity. The decision of whether to test your embryos is a deeply personal one, and understanding the science, benefits, and limitations of PGT-A can help you and your doctor make the most informed choice for your situation.
What Is PGT-A?
Preimplantation genetic testing for aneuploidy is a laboratory procedure that examines embryos created during IVF for chromosomal abnormalities before they are transferred to the uterus. The term "aneuploidy" refers to having an abnormal number of chromosomes. Human cells normally contain 46 chromosomes arranged in 23 pairs. An aneuploid embryo has too many or too few chromosomes, such as an extra copy of chromosome 21, which causes Down syndrome, or a missing chromosome, which typically leads to implantation failure or miscarriage.
PGT-A is distinct from two other types of preimplantation genetic testing:
- PGT-M (for monogenic or single-gene disorders): Tests for a specific known genetic condition such as cystic fibrosis, sickle cell disease, or BRCA mutations.
- PGT-SR (for structural rearrangements): Tests for chromosomal translocations or inversions that one or both parents carry.
How PGT-A Works
The PGT-A process involves several steps that integrate with your IVF cycle:
Embryo Biopsy
On day five, six, or sometimes seven of embryo culture, when the embryo has reached the blastocyst stage, an embryologist removes a small sample of approximately five to ten cells from the trophectoderm, which is the outer layer of cells that will eventually form the placenta. The inner cell mass, which develops into the baby, is left untouched.
This biopsy is performed using a precision laser and a fine pipette under a high-powered microscope. While the idea of removing cells from a developing embryo can sound alarming, research has shown that trophectoderm biopsy at the blastocyst stage does not significantly harm the embryo's viability.
Genetic Analysis
The biopsied cells are sent to a genetics laboratory, where they are analyzed using next-generation sequencing (NGS), the current gold standard technology. NGS can examine all 23 chromosome pairs and detect extra or missing chromosomes with high accuracy. The analysis takes approximately one to two weeks.
Embryo Vitrification
Because the genetic results take time, embryos are vitrified (flash-frozen) after biopsy and stored until results are available. This means PGT-A typically leads to a frozen embryo transfer (FET) cycle rather than a fresh transfer. Given that frozen transfers have success rates comparable to or even exceeding fresh transfers in many situations, this is generally not considered a disadvantage.
Results and Classification
Embryos are classified into one of three categories:
- Euploid: Normal chromosome count. These are considered safe to transfer.
- Aneuploid: Abnormal chromosome count. These are generally not recommended for transfer.
- Mosaic: Contains a mix of normal and abnormal cells. These fall into a gray area that requires careful discussion with your doctor.
Who Benefits Most from PGT-A?
The use of PGT-A has grown dramatically in recent years. In the United States, the proportion of IVF cycles incorporating PGT increased from about 14% in 2014 to approximately 44% by 2019, and usage has continued to rise since then. However, the question of who benefits most remains nuanced.
Advanced Maternal Age
Women over 37 appear to derive the greatest benefit from PGT-A. This is because the rate of chromosomal abnormalities in embryos increases significantly with age. By age 40, an estimated 60 to 80% of embryos may be aneuploid. PGT-A helps these patients avoid transferring embryos that are unlikely to result in a viable pregnancy, potentially reducing the emotional and physical toll of failed transfers and miscarriages.
Recurrent Pregnancy Loss
Couples who have experienced two or more unexplained miscarriages may benefit from PGT-A. While research is still emerging, current evidence suggests that PGT-A may improve live birth rates per transfer in cases of recurrent pregnancy loss by identifying chromosomally normal embryos for transfer.
Recurrent Implantation Failure
Patients who have had multiple failed embryo transfers despite good embryo quality may find that PGT-A helps identify a chromosomal cause. If previous failures were due to aneuploid embryos, selecting a euploid embryo for transfer could change the outcome.
Severe Male Factor Infertility
In cases where sperm quality is significantly compromised, the rate of embryo aneuploidy may be higher. PGT-A can help identify viable embryos in these situations.
The Evidence: What the Research Says
The evidence surrounding PGT-A is more complex than many patients realize, and it is important to understand both what the data supports and where uncertainty remains.
Benefits Per Transfer
The most consistent finding across studies is that PGT-A improves outcomes per embryo transfer. When you transfer a euploid embryo, the implantation rate is higher and the miscarriage rate is lower compared to transferring an untested embryo. This translates to fewer failed transfers and fewer pregnancy losses, which carries significant emotional and physical value.
The accuracy of PGT-A results is high. The misdiagnosis rate after euploid embryo transfer is less than 1%, according to the 2024 ASRM committee opinion. When PGT-A identifies an embryo as aneuploid, that result is also highly reliable.
Cumulative Live Birth Rate
Here is where the conversation becomes more complicated. While PGT-A improves success per transfer, several large randomized controlled trials have found that the cumulative live birth rate, meaning the overall chance of having a baby from a single egg retrieval cycle including all transfers, is similar between PGT-A and conventional IVF.
A pivotal study published in the New England Journal of Medicine found that in women with available blastocysts, overall pregnancy outcomes via frozen embryo transfer were similar whether or not PGT-A was used. This is partly because some aneuploid embryos self-correct, and PGT-A may lead to discarding some embryos that could have resulted in healthy pregnancies.
The 2024 ASRM Position
In 2024, the American Society for Reproductive Medicine (ASRM) issued an updated committee opinion on PGT-A, replacing guidance from 2018. The key takeaway was that the value of PGT-A as a routine screening test for all patients undergoing IVF has not been demonstrated. ASRM acknowledged specific patient populations that may benefit but stopped short of recommending PGT-A universally.
Limitations and Risks to Consider
The Mosaic Dilemma
One of the most challenging aspects of PGT-A is the detection of mosaic embryos, which contain a mixture of chromosomally normal and abnormal cells. Mosaicism is detected in approximately 2 to 40% of biopsied blastocysts depending on the clinic and testing methodology.
The clinical significance of mosaicism is still being understood. Research has shown that some mosaic embryos can result in healthy pregnancies, particularly those with low-level mosaicism (less than 50% abnormal cells) or segmental abnormalities (affecting only part of a chromosome). However, mosaic embryos have lower implantation rates and higher miscarriage rates compared to euploid embryos.
The decision of whether to transfer a mosaic embryo is deeply personal and depends on factors like your age, the number of available embryos, and your willingness to pursue additional cycles. Recent research from 2024 suggests that transferring a mosaic embryo may be a better option than pursuing an additional IVF cycle with PGT-A, particularly for patients over 42.
False Positives and the Biopsy Limitation
PGT-A tests a small sample of trophectoderm cells, not the entire embryo. Because of mosaicism, the biopsied cells may not perfectly represent the embryo as a whole. This means there is a small risk of:
- False positives: An embryo labeled aneuploid may actually be euploid or capable of self-correcting. This could lead to discarding a viable embryo.
- False negatives: An embryo labeled euploid may have aneuploid cells that were not captured in the biopsy, though this is rare.
Reduced Embryo Pool
When the number of eggs retrieved is fewer than 15, research has shown that PGT-A may not significantly improve cumulative live birth rates compared to conventional IVF. For patients with a limited number of embryos, the loss of even one embryo to a potentially inaccurate result can be particularly impactful.
Cost
PGT-A typically adds $3,000 to $6,000 to the cost of an IVF cycle, and it is not always covered by insurance. For patients who are already stretching their finances to afford IVF, this additional expense is a significant consideration.
Emotional Impact
Waiting for PGT-A results adds one to two weeks of uncertainty to an already stressful process. Receiving results showing that most or all of your embryos are abnormal can be devastating. While this information is ultimately useful for planning, the emotional weight of it should not be underestimated.
Questions to Discuss with Your Doctor
If you are considering PGT-A, here are some questions to bring to your next appointment:
- Based on my age and medical history, what percentage of my embryos would you expect to be aneuploid?
- How many blastocysts do you anticipate from my cycle? Is it enough to make PGT-A worthwhile?
- What is your clinic's policy on mosaic embryos?
- Will PGT-A change how you approach my embryo transfer protocol?
- What are the additional costs, and does my insurance cover any portion?
- If I choose not to do PGT-A, how would my treatment plan differ?
Making the Decision
There is no universally right answer about whether to pursue PGT-A. Here are some factors that might tip the scale:
PGT-A may be particularly valuable if you:
- Are 38 or older
- Have experienced recurrent miscarriages or failed transfers
- Want to minimize the chance of miscarriage per transfer
- Have a good expected embryo yield
- Have known risk factors for aneuploidy
PGT-A may be less beneficial if you:
- Are under 35 with no history of fertility issues
- Expect a limited number of embryos
- Are concerned about the additional cost
- Are uncomfortable with the possibility of discarding mosaic embryos
Ultimately, the decision should be made in partnership with your fertility specialist, taking into account your complete medical picture, your values, and your goals for treatment.
A Note on Medical Guidance
This article is for informational purposes only and is not a substitute for professional medical advice. The authors of this blog are not doctors or medical professionals. Always consult with your fertility specialist or healthcare provider before making any decisions about your treatment. Every person's fertility journey is unique, and your doctor can provide guidance tailored to your specific situation.
Conclusion
PGT-A is a powerful tool in the IVF toolbox, but it is not a magic wand. It can provide valuable information about your embryos' chromosomal status, potentially reducing the emotional and physical burden of failed transfers and miscarriages, especially for certain patient populations. At the same time, it has real limitations, it adds cost and time, and it is not proven to improve the overall chance of taking home a baby for all patients. By understanding both the promise and the constraints of PGT-A, you can have a more productive conversation with your doctor and make a choice that feels right for your unique journey.
