Preimplantation genetic testing (PGT) is the genetic analysis of embryos created during IVF before they are transferred to the uterus. By identifying chromosomally healthy embryos, PGT helps selected patient groups achieve pregnancy faster, miscarry less often and avoid passing on serious inherited diseases.
What Is PGT and How Is It Performed?
The process follows six steps:
- 1. Ovarian stimulation: the ovaries are stimulated with medication to mature multiple eggs.
- 2. Egg retrieval and fertilisation: mature eggs are collected and fertilised in the laboratory, usually by ICSI (microinjection).
- 3. Embryo culture: embryos grow in the lab for 5–6 days until they reach the blastocyst stage — the ideal point for biopsy.
- 4. Embryo biopsy: a few cells are taken from the outer layer (trophectoderm) that will form the placenta, without touching the cells that will form the baby. The procedure is performed under the microscope by experienced embryologists.
- 5. Genetic analysis: the cells are sent to a genetics laboratory while the embryos are safely frozen by vitrification.
- 6. Embryo transfer: once results arrive (typically within 1–3 weeks), a genetically normal embryo is thawed and transferred.
PGT-A, PGT-M and PGT-SR: What Is the Difference?
PGT-A — Screening for Chromosome Number
PGT-A (formerly PGS) checks whether an embryo has the normal set of 46 chromosomes. Missing or extra chromosomes (aneuploidy) are the most common cause of failed implantation, miscarriage and conditions such as Down syndrome. PGT-A is particularly relevant for advanced maternal age, recurrent miscarriage and repeated IVF failure — we cover it in depth in our article on PGT-A and who should consider it.
PGT-M — Testing for Single-Gene Diseases
PGT-M detects specific inherited single-gene disorders — for example cystic fibrosis, sickle cell anaemia, thalassaemia and SMA — in embryos of couples known to carry them. It requires genetic counselling first, and a test panel custom-built for the family’s specific mutation.
PGT-SR — Testing for Structural Rearrangements
PGT-SR is used when a parent carries a structural chromosome rearrangement such as a translocation or inversion. Carriers are usually healthy themselves but can produce embryos with unbalanced chromosomes, leading to recurrent pregnancy loss. PGT-SR identifies the embryos with a balanced, healthy chromosome set.
Who Should Consider PGT?
- Women aged 35 and over — chromosomal abnormality rates rise significantly with age
- Couples with two or more miscarriages, since embryonic chromosome errors are their most common cause
- Couples with repeated IVF failures despite good-quality embryos
- Families with a known single-gene disease (cystic fibrosis, thalassaemia, sickle cell anaemia, SMA and others)
- Parents carrying structural chromosome rearrangements (translocation, inversion)
- Selected cases of severe male-factor infertility
- Couples with a previous pregnancy affected by a chromosomal abnormality such as Down syndrome
How Does PGT Affect Success Rates?
PGT does not guarantee success — no test can — but in the right patient groups it meaningfully improves outcomes:
- Higher implantation rates: a chromosomally normal (euploid) embryo implants far more readily than an aneuploid one.
- Lower miscarriage risk: roughly 15–20% of pregnancies end in miscarriage, a large share caused by chromosome errors that PGT-A can screen out.
- Fewer affected pregnancies: PGT-A reduces the risk of chromosomal syndromes, while PGT-M and PGT-SR can prevent transmission of specific inherited diseases.
- Shorter time to pregnancy: selecting the right embryo first avoids transfers that were unlikely to succeed.
- Higher live-birth rates as the combined result of all the above.
One point deserves emphasis: PGT does not change or improve your embryos — it only helps select the healthiest among those you already have. For patients with very few embryos, testing may not add benefit; the decision should always be individualised.
Frequently Asked Questions
Does the biopsy harm the embryo?
In experienced hands the risk is very low. Cells are taken only from the trophectoderm — the future placenta — and modern techniques are optimised to leave the embryo’s development untouched.
Should every IVF couple have PGT?
No. PGT is recommended for couples with specific risk factors. Age, embryo numbers, previous history and genetic risk are weighed together before deciding.
Can PGT detect every genetic disease?
No test can screen for everything. PGT detects the chromosomal abnormalities and the specific single-gene disorders it is designed for; it cannot rule out every possible genetic condition.
How reliable are the results?
Accuracy is high but not absolute. After a PGT pregnancy, your doctor may still recommend standard prenatal tests such as NIPT or amniocentesis for confirmation.
What does PGT cost?
PGT adds to the cost of a standard IVF cycle, varying with the test type (PGT-A, PGT-M or PGT-SR) and the number of embryos analysed. Our team provides transparent, personalised information during consultation.
With more than 30 years of experience, Prof. Dr. Kubilay Vicdan and the Ankara IVF Center team guide couples through every step of genetic testing. Contact us to find out whether PGT is right for you.