Updated by the Progyny Clinical Team — December 2025.
Preimplantation genetic testing (PGT) is used during in vitro fertilization (IVF) to learn more about an embryo before transfer. The testing looks at different genetic information depending on your needs.
- PGT-A checks the number of chromosomes in each embryo.
- PGT-M looks for a known single-gene condition.
- PGT-SR looks for changes in chromosome structure.
Your doctor may recommend one or more tests based on your family history, genetic screening results, or past experiences.
What is PGT-A?
Preimplantation genetic testing for aneuploidy (PGT-A) looks at an embryo’s chromosomes. Most people have 23 pairs of chromosomes, including the sex chromosomes (XX, XY). An embryo with missing or extra chromosomes may have a lower chance of developing into a healthy pregnancy.
Why use PGT-A?
- Helps identify embryos with a normal number of chromosomes
- Supports single embryo transfer and reduces the chance of twins or triplets
What is PGT-M?
Preimplantation genetic testing for monogenic conditions (PGT-M) looks for a known single-gene condition. Each test is customized based on your specific gene change. A genetics lab studies a small cell sample from each embryo to learn whether the embryo is affected, a carrier, or unaffected.
Why use PGT-M?
Your care team may recommend PGT-M if:
- You have a single-gene condition that can be passed directly to a child.
This includes conditions where one gene change is enough to cause the condition (autosomal dominant) or conditions passed on the X chromosome (X-linked).
- You and your partner each carry one copy of the same gene change.
When both copies are passed on, the child may have the condition (autosomal recessive).
How does PGT-M work?
Testing begins before IVF starts.
- You, and the sperm source, provide a DNA sample through blood or cheek swab.
- Sometimes samples from affected family members are needed.
- The genetics lab uses these samples to create a custom test. This step, called probe creation, usually takes six to ten weeks.
Once probe creation is complete, you move forward with IVF.
What is PGT-SR?
Preimplantation genetic testing for structural rearrangements (PGT-SR) looks for changes in chromosome structure, such as translocations or inversions.
Key points
- These changes can be inherited or happen on their own.
- Most people with a balanced rearrangement are healthy and may not know they carry it.
- Carriers of balanced rearrangements have a higher chance of embryos with missing or extra genetic material.
- Balanced rearrangements are chromosome changes in which genetic material is rearranged but not missing or extra, meaning the carrier is typically healthy.
- Embryos with unbalanced rearrangements usually do not result in a live birth. This is because embryos with unbalanced rearrangements have missing or extra pieces of DNA.
- About 5% of recurrent miscarriages are linked to structural rearrangements.
If your history suggests this may be a factor, your doctor may order a blood test called a chromosome analysis (karyotype). Based on those results, PGT-SR may be recommended.
How does PGT work during IVF?
- You complete your IVF cycle. When embryos reach the blastocyst stage (day 5 to 7), the embryologist removes a few cells from the outer layer of each embryo. These cells would form the placenta.
- The biopsy sample goes to a partner genetics lab for testing. The embryos stay frozen in the lab during this process.
- The lab studies the DNA to:
- Check chromosome number (PGT-A).
- Identify embryos not affected by the specific gene condition (PGT-M).
- Screen for a structural rearrangement (PGT-SR).
Because PGT-M looks at a single gene and PGT-A looks at chromosome number, both tests are often used together. Your doctor and embryologist review your results along with embryo quality before choosing an embryo for transfer.
What happens next?
If you have embryos available for transfer, you start a frozen embryo transfer cycle.
- The embryologist selects the embryo based on PGT-A results and, if relevant, PGT-M or PGT-SR findings, plus embryo quality.
- Any remaining embryos stay frozen for future use or may be donated or discarded based on your consent.
- About two weeks after the transfer, you take a pregnancy test to learn whether the embryo implanted.
If you have questions, Progyny is here for you. Please contact your Progyny Care Advocate for support.
Disclaimer: The information provided by Progyny is for educational purposes only and is not medical advice. Always consult a qualified healthcare provider for medical guidance.