Genetic Testing (PGT): Complete Guide to Preimplantation Genetic Testing

The technology feels almost futuristic: testing embryos for genetic conditions before they are even transferred to your uterus, potentially avoiding certain diseases or increasing the chances of a successful pregnancy. When your doctor mentions PGT, it can sound like a solution to uncertainty, a way to stack the odds in your favour.

But like most things in fertility treatment, the reality is more nuanced. Genetic testing of embryos offers genuine benefits in certain situations. It can also add cost, complexity, and new forms of uncertainty. Understanding what PGT can and cannot do helps you make an informed decision about whether it belongs in your treatment plan.

This guide explains the different types of genetic testing, who benefits most, what the process involves, and the limitations you should know about. Because this decision deserves clarity, not just hope.

What Is Preimplantation Genetic Testing?

Preimplantation genetic testing (PGT) refers to testing embryos created through IVF for genetic abnormalities before they are transferred to the uterus. The goal is to identify embryos that are genetically normal or free from specific conditions, improving the chances of a healthy pregnancy.

PGT can only be done with IVF because embryos must be created in the laboratory, biopsied, and tested before transfer. For an overview of IVF and other fertility treatment options, see our Treatments guide.

The Three Types of PGT

PGT-A (Aneuploidy): Tests for the correct number of chromosomes. Humans should have 46 chromosomes (23 pairs). Embryos with extra or missing chromosomes (aneuploidy) often fail to implant, miscarry, or result in conditions like Down syndrome.

PGT-M (Monogenic/Single Gene Disorders): Tests for specific inherited conditions caused by mutations in single genes, like cystic fibrosis, sickle cell disease, or Huntington's disease.

PGT-SR (Structural Rearrangements): Tests for chromosomal structural abnormalities like translocations, where pieces of chromosomes are rearranged. Parents with known translocations are at risk of passing along unbalanced genetic material.

PGT-A: Testing for Chromosome Number

PGT-A is the most commonly discussed form of genetic testing and the one most people are referring to when they talk about "genetic testing" of embryos.

What It Tests For

Every cell should have 46 chromosomes: 22 pairs of autosomes plus either XX (female) or XY (male). Aneuploidy means having the wrong number.

Common aneuploidies include:

• Trisomy 21 (Down syndrome): Three copies of chromosome 21
• Trisomy 18 (Edwards syndrome): Usually fatal
• Trisomy 13 (Patau syndrome): Usually fatal
• Monosomy X (Turner syndrome): Only one X chromosome
• Trisomy of other chromosomes: Usually result in failed implantation or early miscarriage

Most aneuploid embryos do not result in live births. They either fail to implant, miscarry early, or occasionally result in conditions that may or may not be compatible with life.

Who Might Benefit From PGT-A?

This is where the evidence is less clear-cut than many people expect. In its 2024 review, ASRM concluded that the value of PGT-A as a routine test for all IVF patients has not been demonstrated, and the UK's NICE (2026) advises against offering PGT-A to improve live birth rates.

Older women: The proportion of chromosomally abnormal embryos rises with age. In one large study, the chance of having no chromosomally normal blastocyst at all was 2-6% between ages 26 and 37, rising to 33% at 42 and 53% at 44. Some studies suggest PGT-A may help older women, mainly by shortening time to pregnancy and reducing miscarriage per transfer, but this hasn't been proven in high-quality trials that count all patients from the start of treatment.

Recurrent pregnancy loss: Although most early miscarriages are caused by chromosomal problems, studies have not shown that PGT-A improves the chance of a baby for couples with recurrent miscarriage. In one study, couples who simply kept trying naturally conceived as often, and sooner.

Repeated IVF failure: Aneuploidy may be a factor, but the benefit of PGT-A in this group is still uncertain.

Older male partners: ASRM advises that PGT-A should not be done routinely just because the male partner is older.

What PGT-A Can Do

• Identify embryos likely to have the correct chromosome number (euploid)
• Potentially reduce time to pregnancy by avoiding transfer of abnormal embryos
• Possibly lower the miscarriage rate per transfer, although whether this translates into more babies overall is unclear
• Support single embryo transfer: ASRM recommends transferring only one euploid embryo at any age

What PGT-A Cannot Do

• Test for all genetic conditions (only chromosome number, not specific genes)
• Guarantee a healthy baby (many conditions are not chromosomal)
• Guarantee pregnancy (euploid embryos still may not implant)
• Create normal embryos from abnormal ones (it selects, it does not fix)
• Increase the total number of babies from an egg collection: it can only help you choose among the embryos you already have

The Controversy Around PGT-A

PGT-A is not universally recommended. Some controversy exists:

Mosaicism: Some embryos have results showing a mix of normal and abnormal cells. These "mosaic" embryos can implant and lead to apparently healthy babies, although they may implant less often. If they're discarded, some embryos that could have become healthy babies may be lost.

Self-correction and false positives: Some embryos reported as abnormal may in fact be able to develop normally, either because the result was inaccurate or because of correction during development.

Biopsy impact: Removing cells from an embryo is invasive and carries a small risk of damage.

Randomised trials: Two large multicentre trials in women with blastocysts available found overall pregnancy outcomes were similar with and without PGT-A. In one of them, involving 1,212 women aged 20-37, the cumulative live birth rate was 77% with PGT-A and 82% with conventional IVF.

Cost-benefit: PGT-A adds significant cost without a proven increase in the chance of having a baby for most patients.

PGT-M: Testing for Single Gene Disorders

PGT-M is used when one or both parents carry a known genetic mutation that causes a specific inherited condition.

What It Tests For

Single gene disorders are caused by mutations in individual genes. Examples include:

• Cystic fibrosis
• Sickle cell disease
• Thalassemia
• Tay-Sachs disease
• Huntington's disease
• BRCA1/BRCA2 mutations (breast/ovarian cancer predisposition)
• Fragile X syndrome
• Spinal muscular atrophy

The list of conditions that can be tested is extensive and growing.

Who Needs PGT-M?

Known carriers: If you or your partner are known carriers of a recessive condition, there is a 25% chance each embryo will be affected (if both carry it).

Dominant conditions: If one partner has a dominant condition like Huntington's disease, there is a 50% chance of passing it on.

Family history: If there is a family history of a genetic condition, carrier testing followed by PGT-M may be appropriate.

The Process

PGT-M requires more preparation than PGT-A:

1. Genetic counselling: Understanding your specific risks and what testing can offer.
2. Probe development: The lab creates a customised test specific to your mutation. This usually takes several weeks and has an upfront cost.
3. IVF cycle: Embryos are created and biopsied.
4. Testing: The custom probe identifies which embryos are affected, carriers, or unaffected.
5. Transfer: Only unaffected embryos (or unaffected carriers, depending on the condition) are transferred.

What PGT-M Can Do

• Prevent transmission of serious genetic conditions to children
• Provide peace of mind for carrier couples
• Avoid the difficult decision of whether to continue an affected pregnancy

Limitations

• Requires knowing the specific mutation in advance
• Custom test development takes time and money
• Not all conditions can be tested
• Does not test for other genetic issues (though PGT-A can be combined)

PGT-SR: Testing for Structural Rearrangements

PGT-SR is used when one partner carries a chromosomal translocation or other structural rearrangement.

What It Tests For

Translocations: Pieces of chromosomes have swapped places. The carrier is typically healthy (balanced translocation), but their embryos may inherit unbalanced arrangements, causing miscarriage or genetic conditions.

Other rearrangements: Inversions, deletions, duplications, and other structural abnormalities.

Who Needs PGT-SR?

• Individuals diagnosed with a balanced translocation
• Couples who have experienced multiple miscarriages and found a translocation during genetic workup
• Those with a family history suggesting a translocation

What PGT-SR Can Do

• Identify embryos with balanced or normal chromosomes
• Help translocation carriers avoid transferring embryos with an unbalanced rearrangement, which could otherwise lead to miscarriage or a genetic condition

The Biopsy Process

For all types of PGT, cells must be removed from the embryo for testing.

When Biopsy Occurs

Day 5-6 biopsy (blastocyst stage): The most common approach. At this stage, the embryo has two distinct cell types: the inner cell mass (which becomes the baby) and the trophectoderm (which becomes the placenta). Cells are removed from the trophectoderm, leaving the inner cell mass undisturbed.

Day 3 biopsy (cleavage stage): Less common now. Removing cells at this earlier stage, when the embryo has only 6-8 cells, is more impactful and has largely been replaced by day 5 biopsy.

The Procedure

1. A small hole is made in the embryo's outer shell (zona pellucida) using a laser.
2. A small number of trophectoderm cells are gently removed.
3. The cells are sent to a genetics laboratory for analysis.
4. The embryo is vitrified (frozen) while awaiting results.

Safety of Biopsy

Research suggests that properly performed biopsy does not significantly harm embryo development. However, it is an invasive procedure, and a small risk exists. The skill of the embryologist matters.

Results and What They Mean

PGT-A Results

Euploid: Normal chromosome number. Suitable for transfer.

Aneuploid: Abnormal chromosome number. Not recommended for transfer.

Mosaic: Mix of normal and abnormal cells. Decisions here are complex. Mosaic embryos can result in apparently healthy babies, but they may implant less often, and the risks depend on the type and extent of mosaicism. ASRM has published separate guidance on counselling for mosaic results.

No result: Sometimes testing fails, and the embryo status is unknown.

PGT-M Results

Unaffected: Does not carry the condition.

Carrier: Carries one copy of the gene (for recessive conditions, carriers are healthy but could pass the gene on).

Affected: Has the condition.

Decisions about transferring carrier embryos depend on the specific condition and family preferences.

Timing

Results usually take from several days to a few weeks, depending on the laboratory. During this time, embryos remain frozen.

Costs and Practical Considerations

Costs in the UAE

PGT adds significant cost to an IVF cycle. Published figures as of October 2026:

Ask whether the price is per embryo or per cycle, and whether biopsy, freezing and the frozen transfer are included. See our IVF cost guide.

Impact on Cycle Planning

Because results take time, PGT cycles are almost always freeze-all cycles. Fresh transfer is not possible. This means:

• Additional cost of frozen embryo transfer
• Additional time before knowing if pregnancy occurred
• No wasted transfers of abnormal embryos

Embryo Attrition

Not all embryos make it to testing. You might start with 10 eggs and end up with:

• 8 mature eggs
• 6 fertilised embryos
• 3 blastocysts suitable for biopsy
• 2 euploid embryos after testing

This "attrition funnel" is normal but can be emotionally challenging, especially if you end with no euploid embryos.

Making the Decision

Questions to Consider

What is my age? Any benefit of PGT-A is most likely in older women, mainly in time to pregnancy, but it isn't proven to increase the chance of a baby. For younger women, trials show no overall advantage.

What is my history? Recurrent loss or failed transfers are common reasons people consider PGT-A, but evidence of benefit in these groups is still uncertain.

Do we carry known genetic conditions? PGT-M is clearly indicated if so.

How many embryos do we expect? If you are likely to have only 1-2 embryos, testing may not be practical.

Can we afford it? PGT adds significant cost.

How would we feel about the results? Are we prepared for the possibility that no embryos pass testing?

Questions to Ask Your Doctor

• "Do you recommend PGT for my specific situation?"
• "What percentage of embryos at my age are typically euploid?"
• "How do you handle mosaic results?"
• "What are your lab's PGT success rates?"

Key Takeaways

• PGT-A tests chromosome number. It may shorten time to pregnancy for some older women, but it hasn't been shown to improve the overall chance of a baby, and ASRM and NICE don't recommend it routinely.

• PGT-M tests for specific inherited conditions and requires advance preparation with custom probe development.

• PGT-SR is for chromosomal rearrangements like translocations.

• Testing requires embryo biopsy, which is generally safe but adds complexity.

• Not all embryos pass testing, and some results (like mosaicism) require nuanced decision-making.

• PGT adds cost and time. For PGT-A, any benefit is mainly in avoiding transfers that are unlikely to work, not in more babies overall.

• The decision should be individualised based on your age, history, finances, and values.

Sources

• ASRM: The use of preimplantation genetic testing for aneuploidy, a committee opinion (2024) (checked October 2026)
• NICE NG257: Fertility problems: assessment and treatment (March 2026) (checked October 2026)
• HFEA: Treatment add-ons with evidence ratings (checked October 2026)
• Franasiak et al. The nature of aneuploidy with increasing age of the female partner. Fertil Steril 2014 (checked October 2026)
• ASRM: Guidance on the limits to the number of embryos to transfer (2021) (checked October 2026)
• ESHRE/Alpha: The Vienna consensus on ART laboratory performance indicators (2017, PDF) (checked October 2026)

This content is for educational purposes only and should not replace professional medical advice or genetic counselling. Decisions about genetic testing involve complex considerations. Discuss your specific situation with your fertility team and a genetic counsellor.