A Patient's Guide to Preimplantation Genetic Testing (PGT) in IVF

If you're navigating the world of in vitro fertilization (IVF), you've likely encountered a bewildering alphabet soup of acronyms: PGT, PGS, PGD, PGT-A, PGT-M. What do they all mean? And more importantly, which one—if any—is right for you?

Preimplantation genetic testing (PGT) is a powerful technology used during an IVF cycle to screen embryos for genetic or chromosomal abnormalities before they are transferred to the uterus. The goal is straightforward: to select the healthiest available embryo, thereby increasing your chances of a successful pregnancy, reducing the risk of miscarriage, and—in specific cases—preventing the transmission of inherited genetic diseases.[1]

Understanding the Terminology

You may have heard older terms like preimplantation genetic diagnosis (PGD) or preimplantation genetic screening (PGS). These terms are no longer used in modern reproductive medicine. In 2018, the International Society for Preimplantation Genetics renamed all embryo genetic tests under the umbrella term PGT, with different subtypes to reflect their specific purposes.[2] This guide will walk you through each type, how they work, and who benefits most from them.

The Three Types of Preimplantation Genetic Testing

Understanding which type of PGT is relevant to your situation is the first step in making an informed decision. Let's break down each test.

PGT-A: Preimplantation Genetic Testing for Aneuploidy

What it is:
PGT-A (previously known as preimplantation genetic screening or PGS) checks whether an embryo has the correct number of chromosomes. A normal human embryo should have 46 chromosomes—23 from the sperm and 23 from the egg. When an embryo has too many or too few chromosomes, it's called aneuploidy.[3]

Aneuploidy is one of the leading causes of implantation failure, miscarriage, and pregnancy loss. It becomes increasingly common as maternal age increases, particularly after age 35. For example, Down syndrome is caused by an extra copy of chromosome 21 (trisomy 21).

Who is PGT-A for?
PGT-A is recommended for:

Women over age 35 (when the risk of chromosome abnormality increases)
Couples with a history of recurrent miscarriage
Patients with multiple failed IVF attempts
Those seeking to transfer a single embryo with confidence
Couples undergoing IVF for any reason who want to maximize their chances of a successful pregnancy

The goal:
To identify and select a chromosomally normal (euploid) embryo for transfer, improving the chance of a live birth and reducing the likelihood of miscarriage.

Understanding Mosaicism:
It's important to note that some embryos are classified as "mosaic," meaning they contain a mix of normal and abnormal cells. Research shows that some mosaic embryos can still result in a successful pregnancy and birth of a healthy child, though success rates are lower than with fully euploid embryos. Your fertility specialist and genetic counselor can help you understand the implications if your embryo biopsy reveals mosaicism.[4]

PGT-M: Preimplantation Genetic Testing for Monogenic Disorders

What it is:
PGT-M (previously called PGD) is designed to detect a specific single gene disorder that runs in your family. Unlike PGT-A, which looks at chromosome number, PGT-M searches for a known genetic mutation that causes a particular inherited genetic condition.

Examples of single gene disorders that can be screened with PGT-M include:

Cystic fibrosis
Sickle cell anemia
Huntington's disease
Tay-Sachs disease
Duchenne muscular dystrophy
BRCA1/BRCA2 mutations (linked to hereditary breast and ovarian cancer)

Who is PGT-M for?
PGT-M is for individuals or couples who:

Are known carriers of a specific genetic disorder
Have a family history of a genetic condition
Have previously had a child with a genetic disorder
Want to prevent passing on a hereditary genetic disease to their child

Before undergoing PGT-M, couples typically meet with a genetic counselor to confirm the specific genetic mutation they carry. The genetics lab must then develop a customized test (a "probe") for that particular mutation, which requires advance preparation before the IVF cycle.

The goal:
To identify and select embryos that are unaffected by the specific genetic disorder, allowing couples to have a child free from that condition.

PGT-SR: Preimplantation Genetic Testing for Structural Rearrangements

What it is:
PGT-SR is a specialized test for individuals who carry a structural chromosome abnormality—specifically, a translocation or inversion. These are not issues with the number of chromosomes, but rather problems with how genetic material is arranged within the chromosomes.

When one parent carries a balanced translocation (meaning they have the correct amount of genetic material, just rearranged), they are typically healthy. However, their embryos have a very high risk of having an unbalanced amount of genetic material, leading to implantation failure, miscarriage, or—in rare cases—a child with a genetic disorder or developmental abnormality.[5]

Who is PGT-SR for?
PGT-SR is recommended for:

Individuals who have been diagnosed with a chromosomal translocation or inversion (often discovered after recurrent miscarriage)
Couples with a history of multiple pregnancy losses and a known structural rearrangement

The goal:
To select embryos with the correct, balanced amount of genetic material, dramatically reducing the risk of pregnancy loss and increasing the chance of a successful pregnancy.

The PGT Process: How Does Embryo Testing Work?

Regardless of which type of PGT you pursue, the laboratory process follows the same general steps. Understanding this process can help demystify what happens to your embryos and set realistic expectations for your IVF cycle timeline.

Step 1: IVF Cycle and Embryo Development

PGT requires embryos created through in vitro fertilization. After egg retrieval, your eggs are fertilized with sperm in the lab. The resulting embryos are carefully monitored as they develop over the next 5-6 days.

Step 2: Embryo Biopsy at the Blastocyst Stage

On Day 5 or Day 6, when the embryo reaches the blastocyst stage (approximately 100-200 cells), a highly trained embryologist performs an embryo biopsy. Using a laser and micromanipulation tools, they carefully remove 5-10 cells from the trophectoderm—the outer layer of cells that will become the placenta, not the baby.

This biopsy does carry a very small risk (<5%) of damage to the embryo, but decades of research have shown that when performed by experienced professionals, it does not significantly affect embryo viability or the health of the resulting child.[6]

Step 3: Embryo Freezing (Cryopreservation)

After the biopsy, the embryos are immediately frozen using a rapid freezing technique called vitrification. The embryos remain safely cryopreserved until the results of the genetic testing are available.

This means that PGT always involves a frozen embryo transfer (FET) cycle, rather than a fresh transfer. While this adds time to your overall treatment, it allows your body to recover from the stimulation medications and creates optimal conditions for implantation.

Step 4: Genetic Analysis in the Lab

The biopsied cells from the embryo are sent to a specialized genetics laboratory, where they undergo the specific test you've chosen:

PGT-A: Analysis of the number of chromosomes present in an embryo
PGT-M: Testing for a specific genetic mutation
PGT-SR: Evaluation of chromosome structure and balance

Results typically take 1-2 weeks, though timing can vary depending on the complexity of the test.

Step 5: Embryo Selection and Frozen Embryo Transfer

Once the genetic testing results are available, your fertility specialist will review them with you. Embryos identified as normal or suitable for transfer are ranked, and you'll work together to select which embryo to transfer.

In a subsequent frozen embryo transfer cycle—usually your next menstrual cycle or one that fits your schedule—the embryo selected for transfer is carefully thawed and transferred to your uterus. Thanks to modern vitrification techniques, embryo survival rates after thawing exceed 95%.[7]

The Pros and Cons of Preimplantation Genetic Testing

PGT is a powerful tool, but like any medical intervention, it has both benefits and limitations. A truly informed decision requires understanding both sides.

Improved Embryo Selection and Higher Success Per Transfer
By identifying the embryos most likely to result in a successful pregnancy, PGT allows you and your fertility doctor to make more informed decisions about which embryo to transfer. Studies show that transferring a euploid embryo (one with the correct chromosome count) increases pregnancy rates per transfer compared to unscreened embryos, particularly in women over 35.[8]
Reduced Risk of Miscarriage
Aneuploidy—having an abnormal number of chromosomes—is the leading cause of first-trimester pregnancy loss. By screening out aneuploid embryos with PGT-A, you significantly reduce your risk of miscarriage. This can spare you the physical and emotional heartbreak of a failed pregnancy.
Prevention of Genetic Disease Transmission
For couples who are carriers of a known genetic disorder, PGT-M offers the ability to have a biological child who is unaffected by that specific condition. This is the primary and often life-changing benefit of testing embryos for specific genetic disorders.
Confidence in Single Embryo Transfer
Transferring multiple embryos increases the risk of twins or triplets, which carry higher health risks for both mother and babies. PGT allows for elective single embryo transfer (eSET) with confidence, knowing you've selected the embryo with the best chance of success.
Reduced Time to Pregnancy and Cost Savings
While PGT adds an upfront cost, it can prevent the financial and emotional expense of multiple failed transfers, miscarriages, or termination of affected pregnancies. For many patients, it represents a more efficient path to parenthood.

Considerations and Limitations
1. PGT is a Screening Test, Not a Diagnostic Guarantee
  PGT is highly accurate (typically >95%), but it is not 100% perfect. There is a small margin of error, and standard prenatal testing (like amniocentesis or chorionic villus sampling) is still recommended during pregnancy to confirm results.[9]
2. Minimal Risk of Embryo Damage
  While rare, there is a small risk that the embryo could be damaged during the biopsy procedure or during the freezing and thawing process. Centers for reproductive medicine with experienced embryologists minimize this risk.
3. Possibility of No Normal Embryos
  One of the most difficult outcomes is discovering that none of your embryos are suitable for transfer after genetic testing. This is more common in older patients or those with certain reproductive challenges. While heartbreaking, this information can help guide future treatment decisions.
4. Additional Cost
  PGT is an add-on to your IVF cycle, typically costing several thousand dollars. Not all insurance plans cover genetic testing, so it's important to understand the financial commitment.
5. Does Not Test for All Genetic Problems
  PGT-A only looks at chromosome number. PGT-M only tests for the specific genetic mutation you've requested. Neither test screens for every possible genetic defect or chromosomal abnormality. Prenatal genetic counseling and testing remain important even after PGT.

Which PGT is Right for You?

Choosing whether to pursue PGT—and which type—is a deeply personal decision that depends on your medical history, age, and family-planning goals. This simple decision tool can help:

If your primary concern is...	The recommended test is...
Reducing miscarriage risk due to age (35+)	PGT-A (for Aneuploidy)
History of multiple failed IVF cycles or recurrent pregnancy loss	PGT-A (for Aneuploidy)
Preventing a specific inherited disease you or your partner carry (e.g., cystic fibrosis, sickle cell)	PGT-M (for Monogenic disorders)
You have a known chromosomal translocation or inversion	PGT-SR (for Structural Rearrangements)
Maximizing the chance of success per transfer and enabling single embryo transfer	PGT-A (for Aneuploidy)

Your fertility specialist and genetic counselor are your best resources for determining whether PGT makes sense in your unique situation. PGT testing may not be necessary or beneficial for all patients undergoing IVF, particularly younger patients with no history of genetic risks or pregnancy loss.

Conclusion: Is PGT Right for You?

Preimplantation genetic testing represents one of the most significant advances in reproductive medicine. For many patients, PGT provides invaluable information that helps them achieve their dream of a healthy family faster and with less heartache.

However, PGT is not right for everyone, and it's not a guarantee of success. The decision to pursue genetic testing should be based on a thorough discussion with your fertility team, taking into account your age, medical history, genetic background, and personal values.

If you're considering IVF or have questions about whether PGT might benefit your specific situation, we encourage you to speak with one of our experienced fertility specialists. Together, we can create a personalized treatment plan that gives you the best possible chance of bringing home a healthy baby.

Schedule a Consultation with a Fertility Specialist

Frequently Asked Questions

How accurate is PGT testing?

PGT testing is highly accurate, typically exceeding 95% for detecting whole chromosome abnormalities (aneuploidy). However, it's important to understand that PGT is a screening test, not a diagnostic test. The biopsy analyzes only 5-10 cells from the outer layer of the embryo (trophectoderm), which may not always perfectly represent the entire embryo. This is why standard prenatal testing such as NIPT, amniocentesis, or chorionic villus sampling is still recommended during pregnancy.[1][4]

Does embryo biopsy harm the baby?

Decades of research have shown that when performed by experienced embryologists, embryo biopsy at the blastocyst stage does not significantly affect the health of the resulting child or the embryo's ability to implant. The risk of damage to the embryo is very small (less than 5%), and the cells are taken from the trophectoderm (future placenta), not from the inner cell mass that becomes the baby.[6] Multiple studies following children born after PGT have shown no increase in birth defects or developmental issues compared to children conceived through standard IVF.

How much does PGT cost?

The cost of PGT varies depending on the type of testing and your location, but typically ranges from $3,000 to $7,000 in addition to the standard IVF cycle costs. PGT-A (aneuploidy screening) is usually less expensive than PGT-M (monogenic disorders), which requires custom probe development. Insurance coverage for PGT varies widely—some plans cover PGT-M for known genetic conditions, while coverage for PGT-A is less common. We recommend checking with your insurance provider and discussing payment options with your fertility clinic's financial counselor.

Can I do PGT if I'm using donor eggs or donor sperm?

Yes, PGT can be performed regardless of whether you're using your own eggs/sperm or donor gametes. In fact, even with young donor eggs, approximately 15-20% of embryos may still be aneuploid. However, the benefit of PGT-A in donor egg cycles is debated, as younger eggs have lower aneuploidy rates. PGT-M is definitely beneficial if you or your partner (or the donor) are carriers of a known genetic condition.

What if all my embryos come back abnormal after PGT?

Discovering that none of your embryos are suitable for transfer is one of the most difficult possible outcomes of PGT testing. While heartbreaking, this information can be valuable for planning future treatment. Your options may include:

Pursuing another IVF cycle with egg or sperm retrieval
Considering donor eggs or embryos if advanced maternal age is a factor
In some cases, discussing the transfer of low-level mosaic embryos with your doctor and genetic counselor
Exploring alternative family-building options

Your fertility team will help you understand why this occurred and what strategies might improve outcomes in future cycles.

How long does it take to get PGT results?

Results typically take 1-2 weeks after the embryo biopsy, though the timeline can vary depending on the complexity of the test:

PGT-A: Usually 7-14 days
PGT-M: May take 2-4 months, especially if the custom probe needs to be developed
PGT-SR: Similar to PGT-M, typically 2-3 weeks

During this time, your embryos remain safely frozen. Once results are available, you'll schedule a frozen embryo transfer cycle, typically during your next menstrual cycle or at a time that works with your schedule.

Is PGT covered by insurance?

Insurance coverage for PGT varies significantly:

PGT-M: More likely to be covered when there is a documented family history of a genetic disease and both partners are confirmed carriers
PGT-A: Less commonly covered, as it's considered "elective" by many insurance plans
PGT-SR: May be covered if there is a documented chromosomal translocation

We strongly recommend obtaining pre-authorization from your insurance company and working with your clinic's financial team to understand your out-of-pocket costs before proceeding.

Can PGT tell me the sex of my embryo?

Yes, PGT testing analyzes all chromosomes, including the sex chromosomes (X and Y), so the sex of each embryo is determined as part of the testing process. However, clinics have different policies about disclosing this information to patients. Some clinics will share sex information upon request, while others have policies against sex selection for non-medical reasons. The primary purpose of PGT is to identify healthy embryos, not to select embryo sex, and using PGT solely for sex selection raises ethical concerns. Discuss your clinic's policies with your fertility team.

What's the difference between PGT-A and "PGS"?

There is no difference—they are the same test. PGS (Preimplantation Genetic Screening) is the old name for what is now called PGT-A (Preimplantation Genetic Testing for Aneuploidy). The terminology was updated in 2018 by international genetics societies to be more precise and consistent. Similarly, PGD (Preimplantation Genetic Diagnosis) is now called PGT-M (for Monogenic disorders) or PGT-SR (for Structural Rearrangements).[2] If your doctor uses these older terms, they're referring to the same procedures.

Should everyone doing IVF have PGT?

No. While PGT is a powerful tool, it is not appropriate or beneficial for everyone undergoing IVF. Research shows that routine PGT-A for all IVF patients does not necessarily improve overall live birth rates per cycle started.[1] PGT is most beneficial for specific groups:

Women over 35 with higher aneuploidy risk
Couples with recurrent miscarriage
Patients with multiple failed IVF cycles
Known carriers of genetic conditions (for PGT-M or PGT-SR)

Younger patients (under 35) with no history of pregnancy loss or genetic conditions may not see significant benefit from PGT-A and should discuss whether testing is right for their situation.

Scientific References

[1] Practice Committee of the American Society for Reproductive Medicine and Society for Assisted Reproductive Technology. (2024). "The use of preimplantation genetic testing for aneuploidy: a committee opinion." Fertility and Sterility, 122(3), 421-434.
https://www.asrm.org/practice-guidance/practice-committee-documents/the-use-of-preimplantation-genetic-testing-for-aneuploidy-a-committee-opinion-2024/

[2] Preimplantation Genetic Diagnosis International Society (PGDIS). (2022). "PGDIS position statement on the transfer of mosaic embryos 2021." Reproductive BioMedicine Online, 45(1), 19-25.
https://www.rbmojournal.com/article/S1472-6483(22)00106-0/fulltext

[3] Practice Committee and Genetic Counseling Professional Group of the American Society for Reproductive Medicine. (2023). "Clinical management of mosaic results from preimplantation genetic testing for aneuploidy: a committee opinion." Fertility and Sterility, 120(5), 973-982.
https://www.asrm.org/practice-guidance/practice-committee-documents/clinical-management-of-mosaic-results-from-preimplantation-genetic-testing-for-aneuploidy-pgt-a-of-blastocysts-a-committee-opinion/

[4] Greco, E., Minasi, M.G., & Fiorentino, F. (2015). "Healthy babies after intrauterine transfer of mosaic aneuploid blastocysts." New England Journal of Medicine, 373(21), 2089-2090.
https://www.nejm.org/doi/full/10.1056/NEJMc1500421

[5] Capalbo, A., Poli, M., Rienzi, L., et al. (2021). "Mosaic human preimplantation embryos and their developmental potential in a prospective, non-selection clinical trial." American Journal of Human Genetics, 108(12), 2238-2247.
https://www.cell.com/ajhg/fulltext/S0002-9297(21)00412-2

[6] He, H., Jing, S., Lu, C.F., et al. (2019). "Neonatal outcomes of live births after blastocyst biopsy in preimplantation genetic testing cycles: a follow-up of 1,721 children." Fertility and Sterility, 112(1), 82-88.

[7] Cobo, A., García-Velasco, J.A., Coello, A., et al. (2016). "Oocyte vitrification as an efficient option for elective fertility preservation." Fertility and Sterility, 105(3), 755-764.

[8] Rubio, C., Bellver, J., Rodrigo, L., et al. (2017). "In vitro fertilization with preimplantation genetic diagnosis for aneuploidies in advanced maternal age: a randomized, controlled study." Fertility and Sterility, 107(5), 1122-1129.

[9] Munné, S., Kaplan, B., Frattarelli, J.L., et al. (2019). "Preimplantation genetic testing for aneuploidy versus morphology as selection criteria for single frozen-thawed embryo transfer in good-prognosis patients: a multicenter randomized clinical trial." Fertility and Sterility, 112(6), 1071-1079.
https://www.fertstert.org/article/S0015-0282(19)31979-X/fulltext