Fertility & IVF
Preimplantation Genetic Testing (PGT): PGT-A, PGT-M and PGT-SR Explained
Preimplantation genetic testing (PGT) checks a few cells from an IVF embryo before it's transferred to the uterus. There are three main types: PGT-A looks for an abnormal number of chromosomes, PGT-M looks for a specific inherited disease, and PGT-SR looks for chromosome rearrangements. PGT-M and PGT-SR are well established for people at known genetic risk. PGT-A is more debated, and ASRM says the evidence doesn't support using it routinely for all IVF patients.
The three types at a glance
| Type | What it tests | Who it is usually for |
|---|---|---|
| PGT-A (aneuploidy) | Extra or missing chromosomes | People considering ways to choose embryos, often older patients or those with recurrent loss; benefit debated |
| PGT-M (monogenic) | A specific single-gene condition, such as cystic fibrosis, sickle cell disease, Tay-Sachs, or BRCA | Couples who both carry, or one partner has, a known gene variant |
| PGT-SR (structural rearrangement) | Unbalanced pieces of chromosomes | People with a known balanced translocation or inversion |
How it fits into IVF, step by step
- IVF. Eggs are retrieved and fertilized in the lab. See the IVF process step by step.
- Embryo growth. Embryos grow for 5 to 7 days to the blastocyst stage.
- Biopsy. An embryologist removes a few cells from the outer layer (trophectoderm), which becomes the placenta, not the baby.
- Freezing. Embryos are frozen while the cells are tested.
- Results. The lab reports back, usually within a few weeks.
- Frozen embryo transfer of an embryo you choose with your doctor.
What this means for your calendar: PGT means no fresh transfer. You'll wait weeks for results, then do a separate transfer cycle. Many patients say the waiting is the hardest part, especially the daily embryo updates in the first week, when numbers drop at each stage. That attrition is normal, but it's emotionally rough. Not every embryo reaches blastocyst, and some people end up with none to test or none suitable for transfer.
PGT-A: what it can and can't do
Chromosome errors in embryos become more common as the egg's age goes up, and they're a major cause of failed implantation and miscarriage. PGT-A tries to identify embryos with the right number of chromosomes.
What it may offer:
- Help choosing an embryo more likely to implant
- Fewer transfers and less miscarriage for some patients
- Support for single embryo transfer
Its limits:
- ASRM concluded the evidence is insufficient to show PGT-A improves overall live birth rates per IVF cycle started for all patients.
- It doesn't make embryos healthier. It only gives information about embryos you already have.
- False positives happen, meaning a healthy embryo could be labeled abnormal and not used.
- Mosaic results (a mix of normal and abnormal cells) are hard to interpret. Some mosaic embryos have led to healthy births, and clinic policies on transferring them vary.
- It adds cost and requires freezing all embryos.
The right question isn't "Is PGT-A good?" but "Is it likely to help me, given my age, how many embryos I'll probably have, and my history?"
PGT-M: for a known inherited condition
PGT-M is for people who know they could pass on a specific genetic condition. Often that's discovered through carrier screening, which ACOG recommends offering to everyone considering pregnancy, or through family history. In New York, many people learn about it this way for conditions common in their communities, such as Tay-Sachs and other conditions screened for in Ashkenazi Jewish carrier panels, or sickle cell disease.
What to expect:
- Genetic counseling to confirm the risk and go over options
- A custom test designed for your family's specific variant, which can take weeks to set up. Start this early; it can delay your IVF start if you wait.
- IVF with embryo biopsy, then transfer of an unaffected embryo
Other paths include prenatal diagnosis during pregnancy, donor eggs or sperm, or adoption. A genetic counselor can walk you through each.
PGT-SR: for chromosome rearrangements
If you or your partner carries a balanced translocation or inversion, embryos may get an unbalanced amount of genetic material, which can lead to miscarriage or birth defects. PGT-SR identifies embryos that are balanced or normal. This is often found during recurrent pregnancy loss testing.
Common questions
Is the biopsy safe for the embryo? Blastocyst-stage biopsy is the current standard and widely used. Studies so far are reassuring, but long-term data are still being collected, and some experts note the biopsy itself may slightly affect embryo potential. Ask your clinic about its lab's experience.
Do I still need prenatal testing? Yes. PGT isn't 100% accurate. ACOG and ASRM recommend offering standard prenatal screening (such as cell-free DNA) or diagnostic testing (such as CVS or amniocentesis) after PGT, the same as for any pregnancy.
Can PGT tell me everything about my baby's health? No. PGT-A looks at chromosome number, and PGT-M looks for one specific condition. Neither can detect every genetic condition, birth defect or health problem, which is why regular prenatal care and ultrasounds still matter.
The personal questions
PGT raises decisions people don't always expect:
- What will you do with embryos that test abnormal or mosaic?
- How will you choose among several normal embryos?
- Do you want to know the embryo's sex? Clinic policies on sharing this vary.
There are no right or wrong answers, and couples don't always agree at first. It helps to talk these through before results arrive. Counseling can help.
Insurance in New York
New York's IVF mandate requires insured large-group plans to cover three IVF cycles, but DFS guidance doesn't specifically address PGT. Coverage varies, and PGT-M for a known genetic condition may be covered more often than PGT-A. Call your insurer and talk to the clinic's financial counselor before you start. See our New York IVF insurance guide.
Questions to ask your clinic
- What's the specific reason you recommend PGT for me?
- How many embryos do you expect us to have for testing?
- What's your lab's policy on mosaic embryos?
- What happens if no embryos are normal?
- What does testing cost, and is it billed per embryo or per cycle?
- Will I need a genetic counselor visit, and is it covered?
When to see a doctor
Talk with a fertility specialist or genetic counselor about PGT if:
- You or your partner carries a known genetic condition or chromosome rearrangement
- You've had recurrent pregnancy loss
- You're planning IVF and want to know whether PGT-A makes sense for you
- Carrier screening showed you and your partner carry the same condition
Your next step
Find a reproductive endocrinologist in New York, or browse fertility specialists in Manhattan. Bring any carrier screening results and family genetic history to the first visit.
Frequently asked questions
What is PGT-A testing?
PGT-A (preimplantation genetic testing for aneuploidy) checks IVF embryos for an abnormal number of chromosomes. It is used to help choose which embryo to transfer.
Does PGT-A increase IVF success rates?
ASRM has concluded that evidence is insufficient to recommend PGT-A for all IVF patients to improve overall live birth rates. It may reduce the number of transfers and miscarriages for some patients, but it does not create more healthy embryos.
Is PGT-M worth it if I carry a genetic disease?
PGT-M is designed for couples at known risk of passing on a specific inherited condition, such as cystic fibrosis or sickle cell disease. A genetic counselor can help you decide whether it fits your goals.
Do I still need prenatal testing after PGT?
Yes. ACOG and ASRM recommend that prenatal screening or diagnostic testing still be offered after PGT, because PGT results are not 100% accurate.
Does insurance cover PGT in New York?
New York's IVF guidance does not specifically address PGT, so coverage depends on your plan. PGT-M for a known genetic condition is sometimes covered more often than PGT-A. Ask your insurer.
Sources
- ASRM — Indications and management of preimplantation genetic testing for monogenic conditions: a committee opinion
- ASRM — The use of preimplantation genetic testing for aneuploidy: a committee opinion
- ACOG — Preimplantation Genetic Testing (Committee Opinion 799)
- ACOG — Screening for Fetal Chromosomal Abnormalities (Practice Bulletin 226)
This article is for general education and is not medical advice. It does not replace an evaluation by a licensed clinician who knows your history. If you think you have a medical emergency, call 911.