Embryo Genetic Testing (PGT)

Preimplantation genetic testing (PGT) is done on embryos created through ICSI before they are transferred to the uterus, to choose embryos that are genetically or chromosomally healthy.

Types of testing

• PGT-A: detects an abnormal number of chromosomes, such as Down syndrome. This is one of the main causes of implantation failure and early miscarriage, especially as age rises.
• PGT-M: detects a specific genetic disease known in the family, such as thalassemia or spinal muscular atrophy.
• PGT-SR: for couples where one partner carries a structural chromosome change, such as a balanced translocation.

How is it done?

1. ICSI to create the embryos.
2. Embryo culture to day 5 or 6 (the blastocyst stage).
3. A small biopsy of cells from the outer layer of the embryo, the part that later forms the placenta, without touching the cells that form the baby itself.
4. Freezing the embryos by vitrification until the results are ready.
5. Analysis of the samples with modern techniques such as next-generation sequencing (NGS).
6. Transfer of a healthy embryo in a later cycle, after preparing the uterus.

Who is it recommended for?

• Couples who carry a known genetic disease, or who have an affected child.
• Carriers of a structural chromosome change.
• Some cases of recurrent miscarriage or repeated implantation failure, after assessment.
• Some cases where the woman is older.

What to know before starting

• Testing does not guarantee a pregnancy, but it helps choose the most suitable embryo.
• No test is 100% accurate. For genetic diseases, confirming the result during pregnancy is advised.
• Some embryos are "mosaic" and need a specific discussion before any decision.
• Genetic counseling before testing is recommended, to explain the possible results.