How to Interpret PGT-A Results: Euploid, Aneuploid, and Mosaic Embryos Explained

If you have recently received PGT-A results, you may be looking at terms like euploid, aneuploid, and mosaic and wondering what they mean for your embryo transfer. This guide explains the three main result categories in plain English, what each may indicate about an embryo, and how to approach your next steps with your clinical team.

At a glance: PGT-A result categories

• Euploid: The embryo appears to have the expected number of chromosomes (46 in most cases).
• Aneuploid: The embryo has missing or extra chromosomes, which often prevents implantation or leads to miscarriage.
• Mosaic: The embryo has a mix of cells with normal and abnormal chromosome counts.

Your clinician and a genetic counselor can help you understand what your specific results mean in your context.

What is PGT-A?

Preimplantation genetic testing for aneuploidy (PGT-A) is a screening test performed on embryos created through IVF. It checks for the correct number of chromosomes. Chromosomes are structures that carry your genes. Having too many or too few chromosomes can affect whether an embryo implants, develops, or results in a healthy pregnancy.

PGT-A is not a guarantee of a successful pregnancy or a healthy baby. It is one piece of information that can help you and your doctor decide which embryo to transfer.

The three main result categories

Euploid

An embryo is called euploid when the cells tested show the expected number of chromosomes. For a typical embryo, that is 46 chromosomes. Euploid embryos are generally considered to have the best chance of implanting and developing into a healthy pregnancy, but they are not a guarantee. Other factors, such as the embryo’s quality, the uterine environment, and your overall health, also play a role.

Aneuploid

An embryo is called aneuploid when the cells tested show missing or extra chromosomes. For example, an embryo might have 45 or 47 chromosomes. Aneuploid embryos often fail to implant or result in miscarriage. If they do implant, they may lead to conditions such as Down syndrome (trisomy 21) or other chromosomal disorders. Most clinics do not recommend transferring aneuploid embryos, but you should discuss your specific situation with your doctor.

Mosaic

A mosaic embryo has a mix of cells: some with the normal number of chromosomes and some with an abnormal number. The percentage of abnormal cells can vary. Mosaic embryos are sometimes classified as low-level or high-level mosaicism, depending on the proportion of abnormal cells. The meaning of mosaicism is still being studied, and outcomes can vary. Some mosaic embryos may develop into healthy babies, while others may not. Your clinic may offer genetic counseling to help you understand the potential risks and benefits of transferring a mosaic embryo.

How to read your PGT-A report

Your PGT-A report will typically list each embryo and its result. You may see terms like:

• Euploid (or normal)
• Aneuploid (or abnormal)
• Mosaic (with a percentage, e.g., 20% mosaic)
• No result (inconclusive)

It is important to remember that PGT-A tests a few cells from the embryo, not every cell. This means the result may not perfectly reflect the entire embryo. Also, the test itself has limitations, and false positives or false negatives are possible.

What do these results mean for transfer decisions?

Your doctor will consider your PGT-A results along with other factors, such as:

• Your age and medical history
• The number of embryos you have
• The quality of the embryos
• Your previous pregnancy history
• Your personal preferences and values

In general, euploid embryos are prioritized for transfer. Aneuploid embryos are usually not transferred, but there may be exceptions in certain cases. Mosaic embryos are a gray area; some clinics may offer transfer if no euploid embryos are available, but this decision is made on a case-by-case basis.

Questions to ask your clinic

When you receive your PGT-A results, consider asking your doctor or genetic counselor:

• What does this result mean for my specific embryo?
• How reliable is this result?
• What are the chances of implantation and live birth with this embryo?
• Are there any additional tests I should consider?
• What are the risks and benefits of transferring a mosaic embryo?
• How does my age affect the interpretation of these results?

Next steps: a checklist

1. Schedule a follow-up appointment with your doctor to review your results.
2. Ask for a genetic counselor to explain the results in detail.
3. Discuss all your embryo options, including transfer, further testing, or discarding.
4. Take time to consider your options and ask for written information if needed.
5. Make a decision that aligns with your values and medical advice.

Remember, PGT-A is a screening tool, not a guarantee. Your clinical team is there to help you interpret the results in the context of your unique situation.

For more information about PGT in Thailand, see our PGT in Thailand guide. You can also explore our other guides or visit our FAQ page for common questions.

Frequently asked questions

What is the difference between euploid, aneuploid, and mosaic embryos?

Euploid embryos have the expected number of chromosomes (46 in most cases). Aneuploid embryos have missing or extra chromosomes. Mosaic embryos have a mix of cells with normal and abnormal chromosome counts.

Can a mosaic embryo result in a healthy baby?

Some mosaic embryos may develop into healthy babies, but outcomes vary. The percentage of abnormal cells and the specific chromosomes involved can influence the outcome. Your doctor or genetic counselor can provide more personalized information.

Is PGT-A 100% accurate?

No, PGT-A is a screening test and has limitations. It tests only a few cells from the embryo, so it may not reflect the entire embryo. False positives and false negatives are possible.

Should I transfer an aneuploid embryo?

Most clinics do not recommend transferring aneuploid embryos because they often fail to implant or result in miscarriage. However, there may be rare exceptions. Discuss your specific situation with your doctor.

What does 'no result' mean on a PGT-A report?

A 'no result' or inconclusive result means the test could not determine the chromosome status of the embryo. This can happen for technical reasons. Your clinic may offer retesting or discuss other options.

Continue your research

• PGT in Thailand overview
• PGT and IVF guides
• Frequently asked questions

Medical information notice: This article is educational and does not replace individual assessment, diagnosis, genetic counselling or treatment advice from a licensed clinician. Provider services, availability, fees and policies should be verified directly before booking.