What Is PGT? Preimplantation Genetic Testing in IVF, Explained

This guide is written by IRMC’s clinical education team as a plain-language overview of preimplantation genetic testing. It explains what PGT is, how it fits into an IVF cycle, who it may — and may not — help, and its real limitations. Every treatment plan is individual, and any decision should be made with a qualified reproductive specialist and, where relevant, a genetic counselor.

When you read about modern IVF, you will often see the term PGT — preimplantation genetic testing. It is one of the technologies that has changed how clinics select embryos for transfer, especially for patients of advanced age or with a known genetic risk. Yet the terminology can be confusing: PGT-A, PGT-M, and PGT-SR all sound similar, and not every patient needs the same type. This guide explains what PGT is, how it fits into an IVF cycle, who it may help, and the questions worth asking before you proceed.

What Is PGT?

Preimplantation genetic testing (PGT) refers to a set of laboratory procedures that examine embryos created through IVF for specific genetic or chromosomal characteristics before one is transferred to the uterus. The goal is to identify which embryos are most likely to result in a healthy pregnancy, so the clinic and patient can make a more informed transfer decision.

PGT is performed after fertilization and embryo culture, and before transfer. A few cells are gently sampled from each developing embryo (typically at the blastocyst stage), then analyzed while the embryo is safely frozen. The embryo itself is not altered by the test.

The Three Main Types of PGT

• PGT-A (aneuploidy screening). Checks whether an embryo has the correct number of chromosomes. An embryo with too many or too few chromosomes is less likely to implant and more likely to end in miscarriage or, in some cases, a chromosomal condition. PGT-A is the most commonly requested type, particularly for women of advanced maternal age.
• PGT-M (monogenic / single-gene testing). Used when one or both parents are known carriers of a specific inherited single-gene condition, such as cystic fibrosis, thalassemia, or a hereditary neuromuscular disorder. PGT-M checks whether an embryo has inherited the familial mutation, helping reduce the risk of passing the condition to a child.
• PGT-SR (structural rearrangement testing). For patients who carry a balanced chromosomal translocation or inversion. PGT-SR screens embryos for imbalances that can arise from such rearrangements, which are a common cause of recurrent miscarriage.

How PGT Fits Into an IVF Cycle

PGT does not replace the standard IVF steps; it is added at a specific point:

1. Ovarian stimulation and egg retrieval proceed as in a typical cycle, with eggs collected and fertilized (often by ICSI).
2. Embryo culture to blastocyst. Embryos are grown for about five to six days to the blastocyst stage, when a small sample can be taken safely.
3. Biopsy. A few cells are removed from the outer layer of the blastocyst.
4. Vitrification. The biopsied embryo is frozen while the sample is sent for genetic analysis.
5. Analysis and reporting. The laboratory reports each embryo as chromosomally normal, abnormal, or, in some cases, mosaic (a mix of cell lines).
6. Transfer. A normal embryo is thawed and transferred in a later cycle once the uterine lining is ready.

This “freeze-all and transfer later” approach is common because it lets the woman’s body recover from stimulation and allows time for the test results.

Who May Benefit From PGT

PGT is not required for every IVF patient, but it is often considered for:

• Advanced maternal age (commonly 35 and above), where the chance of chromosomal abnormalities in embryos rises with age.
• Recurrent miscarriage (two or more losses), where aneuploidy is a frequent underlying cause.
• Known carriers of single-gene conditions or balanced chromosomal rearrangements, who may benefit from PGT-M or PGT-SR.
• Recurrent implantation failure after transferring apparently good-quality embryos.
• Family history of a specific inherited disorder that the couple wishes to avoid transmitting.

Who May Not Need PGT

Just as important as the list above is being clear about when PGT may add little — and sometimes risk removing usable embryos. A responsible consultation weighs both sides:

• Young patients with a good prognosis. For women under about 35 with normal ovarian reserve and no known genetic risk, the chance that PGT-A changes the outcome may be small relative to its cost, and testing can lead to discarding embryos that might still have resulted in a healthy child.
• Very few embryos. When only one or two embryos are produced, the statistical value of screening drops, and the possibility of discarding the only usable embryo becomes a real concern.
• Ethical or religious considerations. Some patients are uncomfortable with biopsy, freezing, or the discarding of abnormal embryos. These views should guide the plan as much as the medical ones.
• When the result would not change management. If a couple already intends a single embryo transfer and has no specific risk, testing may not alter the clinical path.
• Cost and accessibility. PGT adds laboratory expense and an extra wait. For some, the cost–benefit trade-off does not favor testing.

In short, “doing IVF” and “needing PGT” are not the same decision. The right answer depends on age, diagnosis, embryo number, and personal values — not a default.

Limitations, Accuracy, and the Risk of False Results

No genetic test on an embryo is perfect. Understanding the sources of error is part of informed consent:

• The biopsy samples only the outer cells. PGT takes a few cells from the trophectoderm (which becomes the placenta), not the inner cell mass (which becomes the baby). The two can differ, so the test reflects the sampled cells and may not represent the whole embryo.
• Mosaicism can cause false calls. If an embryo is mosaic — a mix of normal and abnormal cells — the biopsy may over- or under-estimate the abnormality. This can produce a false “normal” (missing an abnormality) or a false “abnormal” (discarding an embryo that could have been viable).
• Technical error and contamination. Like any laboratory test, PGT carries a small risk of sample mix-up, contamination, or analytical error, which is why accredited labs use strict identity and double-verification procedures.
• A “normal” result is not a guarantee. PGT-A reduces the risk of chromosome-related miscarriage but cannot eliminate all pregnancy loss or guarantee a healthy baby. Confirmatory prenatal testing (such as NIPT, amniocentesis, or CVS) remains the standard way to verify a pregnancy.
• Each type has its scope. PGT-A looks at chromosome number, not single-gene disorders (that is PGT-M) or every structural issue. A normal PGT-A result does not rule out all genetic conditions.

Understanding Mosaic Results

When an embryo shows both normal and abnormal cells, it is reported as mosaic. Mosaic findings are common enough that clinics need a clear policy:

• Grading by proportion and type. Mosaic embryos are often described by how much of the sample is abnormal — commonly grouped as low-level (roughly under 20–30%), intermediate, and high-level (over 50%) — and by whether the change affects a whole chromosome or only a segment. Low-level, whole-chromosome mosaics are generally viewed more favorably than high-level or segmental ones.
• Different clinical schools of thought. There is no single global standard. Some centers discard all aneuploid and mosaic embryos; others offer the transfer of low-level mosaic embryos after counseling, on the reasoning that many mosaic embryos self-correct or are confined to the placenta; a third approach is to re-biopsy or re-expand the embryo for clarification before deciding.
• Counseling is essential. Because the evidence is evolving, mosaic results should be discussed with a genetic counselor and your physician, who can explain the specific grade, the center’s policy, and what the options mean for your chances.

Questions to Ask Your Clinic

• Which PGT types does your laboratory offer, and which do you recommend for my case?
• Is the testing performed or reviewed in an accredited genetics laboratory, and what are its reported accuracy and re-biopsy rates?
• What biopsy technique and embryo freezing method do you use, and how do you prevent sample mix-up?
• How are results reported — including mosaic grading — and who explains them to me?
• What is included in the cost, and are there storage fees for biopsied embryos?
• If an embryo comes back mosaic, what is your policy on transfer versus discard?

How IRMC Approaches Third-Generation IVF

The following describes IRMC’s approach; prospective patients are encouraged to verify current accreditations and physician credentials during a consultation.

IRMC (International Reproductive Medicine Center) in Bishkek offers third-generation IVF with preimplantation genetic testing as part of a broader assisted-reproduction program. The embryology laboratory follows U.S.-aligned protocols — including Class-100 laminar-flow workstations, low-oxygen tri-gas incubators, and time-lapse imaging — and applies double verification with barcode traceability at every handling step to reduce the risk of identification error. Each case is reviewed through joint China–U.S. physician consultation, so the decision to use PGT, and which type, is tailored to the individual rather than applied by default. The center welcomes questions about its credentials and encourages patients to confirm any facility’s standing before committing to treatment.

For patients who wish to preserve options before genetic testing or treatment — for example, those facing medical therapy that could affect ovarian function — egg freezing and related preservation services can be coordinated within the same center. Learn more about PGT at IRMC.

Frequently Asked Questions

Does PGT harm the embryo?

The biopsy removes only a few cells from the embryo’s outer layer (which becomes the placenta, not the baby). When performed by experienced embryologists at the blastocyst stage, the procedure is designed to minimize risk to the embryo’s development.

How long does it take to get PGT results?

Testing typically takes one to two weeks from biopsy, after which the care team discusses transfer planning with you.

Can PGT results be wrong?

Any embryo test carries a small chance of a false result, most often because of mosaicism or because the biopsy samples only the placenta-side cells. That is why a normal result is not a guarantee and why confirmatory prenatal testing is still recommended during pregnancy.

Does PGT reveal the sex of the embryo?

Because the test examines chromosomes, the sex is technically visible in the results. Non-medical sex selection is governed by local law and by each clinic’s policy; IRMC discusses PGT strictly on its medical merits. Any questions about what testing can and cannot tell you should be raised with your physician.

Is PGT available for international patients?

Availability and any medical-travel arrangements can be discussed during a consultation. IRMC provides coordination for international patients, including interpretation and follow-up after you return home.

This article is for general information only and is not a substitute for personalized medical advice. PGT options, accuracy, and regulations vary by clinic and by country. Always consult a qualified reproductive specialist and, where relevant, a genetic counselor.

If you are considering IVF with genetic testing, a consultation is the most efficient first step. Book an initial assessment or learn more about the center.