Medically reviewed by Dr. Neha Yadav
During IVF treatment, you may be offered an additional test called PGT-A, or preimplantation genetic testing for aneuploidy. It is often described as embryo genetic screening that can help identify embryos with the right number of chromosomes before transfer.
The purpose sounds straightforward: test the embryos, select the ones most likely to implant and hopefully reduce the chances of miscarriage.
However, an important question remains: Does PGT-A actually increase the chance of having a baby?
The available evidence does not support routine PGT-A for every IVF patient. Large clinical trials have not demonstrated a clear improvement in cumulative live birth rates compared with selecting embryos using their appearance. The test may have a role in selected situations, but its benefits, limitations and potential costs need to be understood before deciding.
What Is PGT-A in IVF?
PGT-A stands for preimplantation genetic testing for aneuploidy. It is a laboratory test used during IVF to assess the number of chromosomes in a small sample of cells taken from an embryo.
Humans normally have 46 chromosomes arranged in 23 pairs. An embryo with an extra or missing chromosome is described as aneuploid. Such embryos may have a lower chance of implantation or may result in pregnancy loss.
PGT-A aims to help identify embryos with an apparently normal chromosome count so that the fertility team can prioritise which embryo to transfer first.
The test is generally performed on embryos that have developed to the blastocyst stage, usually on day 5, 6 or occasionally day 7.
A few cells are removed from the embryo's outer layer, known as the trophectoderm, which contributes to the placenta. The embryo is then frozen while the laboratory analyses the sample.
The result may classify an embryo as:
Euploid: The tested cells show the expected number of chromosomes.
Aneuploid: The tested cells show one or more missing or extra chromosomes.
Mosaic: The sample shows a mixture of cells with different chromosome counts.
A euploid result does not guarantee implantation, pregnancy or the birth of a healthy baby. PGT-A also does not test for every possible genetic condition or birth defect.
What Is the Difference Between PGT-A and PGT-M?
Although both tests are used in IVF, they answer different questions.
| Feature | PGT-A | PGT-M |
|---|---|---|
| What it checks | The number of chromosomes | A specific known genetic condition |
| Main purpose | Helps prioritise embryos based on chromosome count | Checks whether an embryo carries a particular inherited condition |
| Example | Identifying an embryo with an extra or missing chromosome | Testing for a known inherited condition such as thalassaemia |
PGT-M may be discussed when one or both parents carry a known genetic condition that could be passed on to their child.
You can read more about preimplantation genetic testing for families at risk of thalassaemia.
The important distinction is that PGT-A examines chromosome numbers, while PGT-M looks for a specific known genetic change.
Does PGT-A Increase IVF Success Rates?
This is the most important question to discuss before agreeing to the test.
PGT-A can help rank embryos for transfer based on the chromosome results from the sampled cells. However, ranking embryos is not the same as increasing the total number of babies born from an IVF cycle.
Large randomised trials have not demonstrated a clear improvement in cumulative live birth rates with routine PGT-A compared with selecting embryos by appearance.
What Did the Largest Clinical Trial Find?
A major randomised trial published in the New England Journal of Medicine in 2021 included 1,212 women aged 20 to 37 who had at least three good-quality blastocysts.
The researchers compared embryo selection using PGT-A with selection based on embryo appearance.
The cumulative live birth results after up to three embryo transfers were:
PGT-A group: 77.2%
Without PGT-A: 81.8%
The study did not demonstrate a higher cumulative live birth rate with PGT-A. Selecting embryos by appearance was found to be non-inferior in this study population.
However, the findings should be interpreted in context. The trial involved women with several good-quality blastocysts, and its results should not automatically be applied to every age group or IVF situation.
What Did the STAR Trial Find?
The STAR trial, published in 2019, included 661 women aged 25 to 40.
It compared PGT-A with embryo selection based on morphology, meaning the embryo's appearance and development.
The ongoing pregnancy rate per woman randomised was:
PGT-A group: 41.8%
Morphology-only group: 43.5%
There was no clear overall improvement with PGT-A.
A later analysis suggested a possible advantage per transfer among women aged 35 to 40. However, this was a post-hoc finding and was not statistically significant when all randomised women were considered.
This distinction matters: a higher pregnancy rate per transfer does not necessarily mean a higher chance of having a baby from the entire IVF cycle.
Does PGT-A Reduce the Risk of Miscarriage?
PGT-A may help reduce the chance of transferring an embryo with an abnormal chromosome count. Since some chromosome abnormalities are associated with pregnancy loss, selecting an embryo with a euploid result may reduce miscarriage risk per transfer in certain circumstances.
However, fewer miscarriages do not automatically mean more live births.
There are several reasons:
Some embryos classified as abnormal may still have reproductive potential.
A biopsy samples only a small number of cells from the embryo.
A test result does not guarantee that the entire embryo has the same chromosome pattern.
Some embryos may be set aside even though they could potentially have resulted in a pregnancy.
The UK Human Fertilisation and Embryology Authority (HFEA) has rated PGT-A differently depending on the outcome being considered. Its published ratings distinguish between the chance of having a baby and the possibility of reducing miscarriage.
Therefore, ask your fertility specialist which outcome is expected to improve in your particular situation.
Can PGT-A Be Useful for Women Above 35 or 38?
The proportion of embryos with an abnormal chromosome count generally increases with maternal age. This is one reason PGT-A may be discussed more frequently with women in their late thirties and beyond.
The American Society for Reproductive Medicine (ASRM) has noted that PGT-A may have a beneficial role for some women of advanced maternal age, particularly when several blastocysts are available.
However, the evidence is not strong enough to recommend it routinely for every older patient.
The potential benefit may be more about prioritising an embryo and reducing the number of unsuccessful transfers rather than increasing the total chance of a live birth.
The number of embryos available also matters. If you have only one or two blastocysts, testing may not provide the same selection advantage as it might when several embryos are available.
You may find our guide on how many eggs are considered a good number at your age helpful when discussing your IVF treatment plan.
What Is a Mosaic Embryo? Can It Be Transferred?
A mosaic embryo is one in which the tested sample contains a mixture of cells with different chromosome counts.
For example, some sampled cells may show the expected chromosome number while others show an extra or missing chromosome.
A mosaic result does not necessarily mean that every cell in the embryo has the same abnormality.
This is important because the biopsy examines only a small sample from the embryo's outer layer. It does not directly examine every cell that may contribute to the developing baby.
Research published in 2026 involving 9,828 single-embryo transfers found that embryos with intermediate results commonly reported as mosaic had a lower live birth rate than embryos classified as euploid. The study also raised questions about whether mosaic reporting improves embryo selection.
Mosaic embryos should therefore not automatically be treated as having no reproductive potential.
Whether a mosaic embryo can be considered for transfer depends on the specific result, the laboratory report, clinical circumstances and appropriate genetic counselling.
If you receive a mosaic result, ask your fertility specialist:
What type of mosaic result was reported?
What does the result mean for this particular embryo?
What are the possible reproductive outcomes?
Is genetic counselling recommended?
What prenatal testing would be discussed if pregnancy occurs?
What Are the Risks and Limitations of PGT-A?
PGT-A can provide additional information, but it is not a perfect test. It also introduces additional steps into the IVF process.
1. Embryo Biopsy
PGT-A requires a few cells to be removed from the embryo's outer layer.
Although embryo biopsy is an established laboratory procedure, the potential effect of removing cells is not fully understood in every situation. The HFEA also warns that biopsy may damage an embryo.
2. Results May Not Represent Every Cell
The test analyses a small sample rather than the entire embryo.
This is particularly relevant when a result is mosaic or difficult to classify. A result from the sampled cells may not perfectly represent the chromosome pattern of all cells in the embryo.
3. Potentially Viable Embryos May Be Set Aside
One important concern is that embryos classified as abnormal may sometimes still have reproductive potential.
The ASRM has highlighted the possibility that clinics could discard embryos that might otherwise have resulted in healthy births.
Before testing, ask your clinic to explain its written policy for embryos reported as aneuploid or mosaic.
You can also read about what happens to unused embryos in India and the available choices.
4. You May Have No Embryo Available for Transfer
If every embryo receives an abnormal result, the clinic may not have an embryo it considers suitable for transfer.
This can be emotionally difficult, particularly after the time, expense and effort involved in an IVF cycle.
It is important to understand this possibility before consenting to PGT-A.
You can read our guide on what may happen after a failed IVF cycle.
5. It Can Delay Embryo Transfer
Because the embryo is generally frozen while the biopsy sample is tested, the transfer usually takes place in a later cycle.
This means PGT-A may add time to the treatment process. Ask your clinic how long results typically take and when a frozen embryo transfer could be planned.
6. Additional Cost
PGT-A is an additional expense on top of the IVF cycle.
The total cost may involve:
Embryo biopsy.
Genetic testing for each embryo.
Embryo freezing.
Storage, where applicable.
A later frozen embryo transfer.
Ask for an itemised estimate in writing before consenting. The cost should be considered alongside the possible benefit for your individual circumstances.
Is PGT-A Allowed in India?
Indian law places specific restrictions on genetic testing and sex selection during assisted reproductive treatment.
Section 25 of the Assisted Reproductive Technology (Regulation) Act, 2021 states that pre-implantation genetic testing is to be used to screen embryos for known, pre-existing, heritable or genetic diseases.
How this provision applies to chromosome-count screening such as PGT-A is a legal and regulatory question that should be clarified with the clinic and its legal adviser.
The law also prohibits sex selection. Under the ART Act and the Pre-conception and Pre-natal Diagnostic Techniques (Prohibition of Sex Selection) Act, 1994, determining or selecting a child's sex is prohibited, subject to the specific legal provisions for sex-linked disease diagnosis and treatment.
PGT-A must not be used as a way to choose a boy or a girl. Embryo sex selection is not an option in India.
Should You Choose PGT-A Before IVF Embryo Transfer?
There is no single answer for every couple. The decision should depend on age, embryo numbers, previous pregnancy history, treatment goals and the evidence available.
| PGT-A may be discussed when… | Routine PGT-A is not supported when… |
|---|---|
| You are in your late thirties or older and have several blastocysts | You are under 35 with a normal prognosis |
| You have experienced repeated pregnancy losses, including a confirmed chromosomal loss | You have only one or two embryos available |
| Several individual embryo transfers may otherwise be needed | Donor eggs are being used, where evidence does not support routine use |
| You understand the limitations and possible consequences of the result | The only explanation offered is that the clinic uses it for everyone |
For women with repeated pregnancy loss, PGT-A may be discussed as an option in selected circumstances. However, definitive evidence that it improves the overall chance of a baby in this group remains limited.
Similarly, PGT-A should not be presented as a guaranteed way to improve IVF success.
Before agreeing to the test, ask your clinic to explain its embryo-selection policy, including how it handles mosaic and abnormal results.
What Questions Should You Ask Before Agreeing to PGT-A?
Before making a decision, consider asking your fertility specialist:
What specific benefit do you expect PGT-A to provide in my situation?
Does the evidence support its use for someone of my age?
How many blastocysts do I have available for testing?
What happens if an embryo is reported as mosaic?
What is your written policy for embryos classified as abnormal?
Could an embryo be set aside even if it might have reproductive potential?
How much will the biopsy, testing, freezing and later transfer cost?
How long will I have to wait for the results?
Will prenatal testing still be recommended if I become pregnant?
A particularly useful question is:
"Which outcome will PGT-A improve for someone my age with my number of embryos, and what is the possibility of setting aside an embryo that could have worked?"
Frequently Asked Questions
1. Does PGT-A Increase IVF Success Rates?
The largest randomised trials have not demonstrated a clear improvement in cumulative live birth rates with routine PGT-A compared with selecting embryos based on appearance. It may help prioritise embryos for transfer in selected situations, but it does not create additional embryos or guarantee a baby.
2. Does PGT-A Reduce Miscarriage?
PGT-A may reduce the chance of transferring an embryo with certain chromosome abnormalities and may reduce miscarriage risk per transfer in some circumstances. However, a lower miscarriage risk does not automatically mean a higher cumulative live birth rate.
3. What Is a Mosaic Embryo, and Can It Be Transferred?
A mosaic embryo has a mixture of chromosome patterns in the tested sample. Some mosaic embryos have resulted in healthy births, but their reproductive potential varies. A fertility specialist and genetic counsellor should explain the individual result and whether transfer can be considered.
4. What Is the Difference Between PGS and PGT-A?
PGS was the earlier term for preimplantation genetic screening. The terminology changed to PGT-A to describe testing for aneuploidy, or an abnormal number of chromosomes. PGT-M is different because it tests for a specific known genetic condition.
5. How Much Does PGT-A Cost in India?
PGT-A is generally an additional expense alongside IVF. The total estimate may include biopsy, testing per embryo, freezing and a later frozen embryo transfer. Costs vary between clinics and laboratories, so request an itemised written estimate before making a decision.
6. Will PGT-A Tell Me the Sex of My Embryo?
PGT-A examines chromosome numbers, but embryo sex selection is prohibited in India. The ART Act and PCPNDT Act restrict determining or selecting a child's sex, subject to specific legal provisions relating to sex-linked diseases. PGT-A should not be used for choosing a boy or a girl.
Conclusion
PGT-A is a tool for assessing chromosome numbers in a small sample of embryo cells. It can help fertility specialists prioritise embryos for transfer, but it does not improve the embryos themselves.
The strongest available trial evidence has not demonstrated a clear increase in cumulative live births with routine PGT-A. Its potential role may be more relevant for selected older women with several blastocysts or particular pregnancy histories, but the benefits are not guaranteed.
The test also has limitations, including biopsy-related concerns, uncertain mosaic results, the possibility of setting aside embryos with reproductive potential, additional costs and delays before transfer.
Before deciding, discuss your age, embryo numbers, previous pregnancy history and treatment goals with your fertility specialist. Ask what PGT-A is expected to change in your specific case rather than assuming that additional testing always means a better outcome.
Medical Review: Dr. Neha Yadav — View Doctor Profile
This article is for general educational purposes and does not replace individual medical advice. Please consult a qualified fertility specialist about your own situation.