What does PGT-A test, and how?
PGT-A stands for preimplantation genetic testing for aneuploidy. It checks whether an embryo has the normal number of chromosomes. A typical human cell has 46 chromosomes, in 23 pairs. An embryo with a missing or extra chromosome is called aneuploid. Most aneuploid embryos do not implant, or they end in miscarriage.
The test works in four steps:
- Growth. The embryo grows in the lab to the blastocyst stage, on day 5 or 6.
- Biopsy. An embryologist removes a few cells from the trophectoderm, the outer layer that becomes the placenta. The inner cell mass, which becomes the baby, is not touched.
- Freezing. The embryo is frozen while the cells are sent to a genetics lab.
- Report. The lab counts the chromosomes in the sample and reports a result for each embryo, usually within a few weeks.
Timing matters in surrogacy. If you plan to test, test before you match. Your PGT-A results go into your profile, they tell you how many euploid embryos you have to plan around, and they let the surrogate decide with full information. Embryos that are already frozen untested can usually be thawed, biopsied and refrozen, though this adds a step and a small risk to each embryo, so ask your clinic.
PGT-A does not look for specific genetic diseases, and it does not report on how the embryo looks. Grading does that. See embryo quality and grading.
What do euploid, aneuploid and mosaic results mean?
Each tested embryo gets one of four results.
| Result | Meaning | Typical clinic transfer policy | Note for surrogacy |
|---|---|---|---|
| Euploid | Normal number of chromosomes in the sample | Transferred first | The result most surrogates and clinics prefer for a gestational carrier |
| Aneuploid | Abnormal number of chromosomes | Not transferred | Avoids a transfer unlikely to succeed and a likely miscarriage |
| Mosaic | A mix of normal and abnormal cells in the sample | Some clinics transfer selected mosaics after genetic counseling; others do not | The surrogate's consent and the agreement should address it |
| No result | The lab could not read the sample | Often rebiopsied or treated as untested | Discuss with your clinic before match |
A euploid result is a strong signal, not a guarantee. The biopsy samples a few cells from the placenta-forming layer, which does not always reflect the whole embryo, and a small rate of false results exists. Prenatal screening during the pregnancy still applies.
A mosaic result needs a conversation with your clinic and a genetic counselor. If you would consider transferring a mosaic embryo, tell PLS before matching. The surrogate needs to know and agree, and the gestational carrier agreement should say so.
Why is PGT-A common in surrogacy specifically?
Because each failed transfer in surrogacy costs more than in ordinary IVF: more time, more money, and another person's body.
PGT-A is widely used before a surrogacy transfer because, by excluding aneuploid embryos, it raises the live birth rate per transfer and lowers the miscarriage rate per transfer. That matters more when:
- Another person carries the pregnancy. Each transfer means medications, monitoring visits, travel to your clinic, and for a miscarriage, a loss your surrogate goes through physically.
- Each transfer is expensive. A failed transfer in surrogacy costs months and roughly $5,000 to $10,000 in clinic fees, plus surrogate payments. Estimate; ranges vary by clinic.
- Time is part of the cost. A new cycle usually takes 2 to 3 months.
Testing does not create more viable embryos. It helps you avoid spending a transfer, and a surrogate's months, on an embryo that was unlikely to lead to a birth. For what happens after a negative test or a loss, see failed transfer and miscarriage.
What does PGT-A cost?
PGT-A costs about $3,000 to $6,000 per batch of embryos, plus the biopsy and freezing fees. These are estimates; ranges vary by clinic and lab.
Clinics price PGT-A in different ways. Some charge per embryo, some per batch, and some bundle the biopsy into the IVF cycle fee. Ask for a written quote that separates:
- The biopsy fee.
- The lab's testing fee, per embryo or per batch.
- Freezing and storage.
- Any genetic counseling.
PGT-A is paid to your fertility clinic or the genetics lab directly, not through Private Label Surrogacy (PLS) or escrow. It is part of your IVF budget. See IVF costs in surrogacy.
What does ASRM say about its limits?
ASRM's committee opinion on PGT-A sets out what the test can and cannot do. In plain terms:
- PGT-A does not increase the number of viable embryos. It identifies which embryos are likely aneuploid. The euploid embryos were euploid before testing.
- It improves outcomes per transfer, not necessarily per retrieval. Your overall chance of a baby from one egg retrieval depends on how many euploid embryos that retrieval produced.
- The benefit is clearest when the egg source is over 35, because the share of aneuploid embryos rises with egg age.
- The biopsy carries a small risk to the embryo, and results are not perfect.
ASRM does not recommend PGT-A as routine for every IVF patient. Surrogacy is a setting where many clinics and parents choose it anyway, because the cost of each transfer is higher. Discuss your own case with your reproductive endocrinologist.
Questions that help you decide:
- How old was the egg source at retrieval? The older the eggs, the more likely some embryos are aneuploid.
- How many blastocysts do you have? With many embryos, testing helps you choose. With one or two, it may tell you whether you need another retrieval before you match.
- Have you had a failed transfer or a miscarriage before?
- Does your clinic, or the surrogate you hope to match with, prefer tested embryos?
- What would you do with a mosaic result?
Do surrogates or clinics require it?
PGT-A is not required by law. Whether it is required in practice depends on your clinic and your surrogate.
- Clinics. Many clinics prefer euploid embryos for transfer into a gestational carrier. Some require it. Ask your clinic for its policy.
- Surrogates. Many surrogates ask for euploid embryos in their matching criteria. At PLS, embryo status is part of your profile, and a surrogate who wants tested embryos is matched with parents who have them.
- Agreements. The gestational carrier agreement records what embryos will be transferred, including whether a mosaic embryo may be.
If your embryos are untested, you can still match. Some surrogates are comfortable with untested embryos, particularly from a younger egg source. It may narrow the pool and add time. For how embryo status fits with other criteria, see how surrogate matching works.
PGT-A versus PGT-M and PGT-SR
PGT-A is one of three types of preimplantation genetic testing.
- PGT-A (aneuploidy) checks the number of chromosomes. It is a screening test used for many IVF patients.
- PGT-M (monogenic) tests for a specific single-gene condition that runs in a family, such as cystic fibrosis or sickle cell disease. It requires genetic work-up of the parents or donors beforehand and is designed for that family.
- PGT-SR (structural rearrangements) tests for unbalanced chromosome rearrangements when a parent or donor carries a balanced translocation or another structural change.
PGT-M and PGT-SR are ordered when there is a known genetic reason. They are often run alongside PGT-A on the same biopsy. Your clinic's genetic counselor advises which, if any, apply to you.
Sources
- ASRM (American Society for Reproductive Medicine), Practice Committee opinion on the use of preimplantation genetic testing for aneuploidy (PGT-A). https://www.asrm.org
- SART (Society for Assisted Reproductive Technology). https://www.sart.org