Understanding Mosaic Embryos in PGT-A Results: A Guide for Patients in Thailand

If you have received PGT-A results that describe an embryo as “mosaic,” you may be wondering what that means for your IVF journey. In simple terms, a mosaic embryo has a mix of cells with normal chromosomes and cells with abnormal chromosomes. This is different from a uniformly normal (euploid) embryo or a uniformly abnormal (aneuploid) embryo. Understanding your results is the first step in making informed decisions, but it is important to remember that every situation is unique and should be discussed with your fertility team.

At a Glance: Key Points About Mosaic Embryos

• Mosaic embryos contain both normal and abnormal cells.
• Mosaicism is reported as a percentage or a level (low, medium, high).
• Mosaic embryos may have the potential to develop into healthy babies, but outcomes vary.
• Your clinic will consider the specific mosaic level and which chromosomes are involved.
• Always ask your clinic for a detailed explanation of your results and your options.

What Is a Mosaic Embryo?

During embryo development, cells divide and sometimes errors occur in chromosome distribution. A mosaic embryo has a mixture of cells: some with the correct number of chromosomes (euploid) and some with an incorrect number (aneuploid). This is different from a non-mosaic embryo, where all cells have the same chromosomal status.

Mosaicism can be detected through preimplantation genetic testing for aneuploidy (PGT-A), which analyzes a small sample of cells from the embryo. The test reports the proportion of abnormal cells, often as a percentage. For example, a result might say “20% mosaic” or “low-level mosaic.”

How Are Mosaic Results Reported?

PGT-A results typically categorize embryos as:

• Euploid: all cells appear to have the normal number of chromosomes.
• Aneuploid: all cells appear to have an abnormal number of chromosomes.
• Mosaic: a mix of normal and abnormal cells.

Mosaic results may be further described by the level of mosaicism (low, medium, high) and the specific chromosomes involved. Some laboratories report a percentage, such as “30% mosaic.” It is important to ask your clinic for a clear explanation of the terminology they use.

What Does a Mosaic Result Mean for Transfer?

The decision to transfer a mosaic embryo is complex and depends on many factors. Some studies suggest that mosaic embryos can result in healthy live births, but the risk of an abnormal pregnancy may be higher than with a euploid embryo. However, the exact risks are not fully known, and outcomes vary.

Your fertility team will consider:

• The specific level of mosaicism (low, medium, high).
• Which chromosomes are affected.
• Whether the abnormality is likely to be tolerated or cause health issues.
• Your medical history and previous IVF outcomes.
• Your personal preferences and values.

Some clinics may recommend transferring a mosaic embryo if no euploid embryos are available, while others may advise against it. There is no universal rule, so it is essential to have a detailed discussion with your doctor.

Questions to Ask Your Clinic About Mosaic Embryos

When you receive mosaic results, consider asking your clinic the following questions:

• What is the exact level of mosaicism in this embryo?
• Which chromosomes are involved, and what is the potential impact?
• What is your clinic’s policy on transferring mosaic embryos?
• Are there any additional tests or consultations recommended?
• What are the potential risks and benefits of transferring this embryo?
• What is the likelihood of a healthy live birth with this embryo compared to other options?
• Are there any follow-up tests during pregnancy that you would recommend?

Next Steps: Making an Informed Decision

After receiving mosaic results, take time to process the information and gather all the facts. Here is a simple checklist:

1. Request a written copy of your PGT-A results and a detailed explanation.
2. Schedule a consultation with your fertility specialist to discuss the findings.
3. Ask about the specific chromosomes involved and the level of mosaicism.
4. Discuss all available options, including transferring the mosaic embryo, further testing, or considering other embryos.
5. Consider seeking a second opinion if you have any doubts.
6. Take time to make a decision that feels right for you and your family.

Remember, a mosaic result does not automatically mean an embryo is unusable, but it does require careful consideration. Your fertility team is there to guide you through the process.

Understanding PGT-A Limitations

PGT-A is a screening test, not a guarantee of a healthy baby. It cannot detect all genetic conditions, and the biopsy sample may not perfectly represent the entire embryo. Mosaicism itself can be challenging to interpret, and the technology has limitations. It is important to understand that PGT-A results are one piece of information in your decision-making process.

For more information about PGT in Thailand, you can visit our PGT in Thailand page. For general guides, see our Guides section. If you have specific questions, check our FAQ.

Frequently asked questions

What is a mosaic embryo?

A mosaic embryo has a mix of cells with normal chromosomes and cells with abnormal chromosomes. This is different from a uniformly normal (euploid) or uniformly abnormal (aneuploid) embryo.

How is mosaicism reported in PGT-A results?

Mosaicism is often reported as a percentage or a level (low, medium, high). The report may also indicate which chromosomes are affected. Your clinic can explain the specific terminology used.

Can a mosaic embryo lead to a healthy baby?

Some studies suggest that mosaic embryos can result in healthy live births, but outcomes vary. The risk of an abnormal pregnancy may be higher than with a euploid embryo, but it is not guaranteed. Discuss your specific situation with your doctor.

Should I transfer a mosaic embryo?

The decision depends on many factors, including the level of mosaicism, which chromosomes are involved, your medical history, and your preferences. There is no universal answer, so it is important to have a detailed discussion with your fertility team.

What questions should I ask my clinic about mosaic results?

Ask about the exact level of mosaicism, which chromosomes are affected, the clinic's transfer policy, potential risks and benefits, and any recommended follow-up tests during pregnancy.

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.