Preimplantation genetic testing (PGT)

⚕ Medically reviewed by Prof. Stratis Kolibianakis, MD, MSc, PhD · Thessaloniki Medical Chamber Reg. No. 16340 · Last reviewed 6 July 2026

We apply preimplantation genetic testing at the blastocyst stage before transfer. PGT-A screens for chromosomal aneuploidies. The test can be done in women aged 38 or older, in women with two or more miscarriages, or in three or more failed IVF attempts. PGT-M detects specific inherited monogenic conditions when one or both parents are known carriers. PGT-SR detects structural chromosomal rearrangements (e.g. translocations, inversions) in known carriers. PGT-HLA selects embryos that are HLA-compatible with a sick sibling who needs a transplant. We perform trophectoderm biopsy on day 5–6 and send the sample to an accredited genetics laboratory. See in our calculator how PGT-A changes the chance of pregnancy.

Regulatory framework in Greece (Layer 0). PGT-HLA (“saviour sibling”) is not applied automatically: it requires case-specific authorisation from the Greek National Authority of Assisted Reproduction, with a documented medical indication for the affected sibling. We explain the authorisation pathway and the paperwork required before the cycle begins. The other forms of PGT (A/M/SR) are also applied in accordance with Greek assisted-reproduction law.

What PGT-A can and cannot tell you. PGT-A checks whether an embryo has the correct number of chromosomes. It can lower the miscarriage risk per transfer and shorten the time to a healthy pregnancy in selected patients, by selecting a euploid embryo to transfer. It does not, however, increase the total number of healthy embryos you have — it does not “make” better embryos, it only sorts them. In women with few embryos the benefit may be limited, and a “borderline” (mosaic) result needs specialist genetic counselling. That is why the decision to use PGT-A is individualised.

PGT-M and PGT-SR: for whom. PGT-M is for couples who are known carriers of a serious monogenic disease (e.g. cystic fibrosis, beta-thalassaemia, Huntington’s disease) and wish to avoid transmitting it. PGT-SR is for carriers of a balanced chromosomal rearrangement that causes recurrent miscarriage or failed transfers. Both are preceded by genetic counselling and a custom test design before the IVF cycle.

The process step by step. PGT requires an IVF cycle to create embryos in the laboratory. On day 5–6 we take a few cells from the trophectoderm (the part that will form the placenta, not the baby), the embryos are frozen, and the sample is sent to an accredited laboratory. Embryo transfer takes place in a later cycle, once results are back. Biopsy performed by an experienced embryologist does not reduce implantation chances.

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