PGD / PGT Genetic Testing

PGT-A, PGT-M and PGT-SR explained

PGD is the older term; PGT is the current one. What matters is which test is being discussed, because they answer different questions.

• PGT-A checks whether an embryo has the expected number of chromosomes. Embryos with the wrong number often fail to implant or miscarry.
• PGT-M looks for one specific inherited single-gene condition that a couple is known to carry, such as thalassaemia or cystic fibrosis.
• PGT-SR is used where a parent carries a structural chromosome rearrangement, such as a translocation, which can produce unbalanced embryos.

Who embryo testing may help

• Couples with a known inherited condition in the family, confirmed by carrier testing
• Recurrent pregnancy loss, particularly where chromosomal causes are suspected
• Repeated implantation failure across several IVF cycles
• Advanced maternal age, where chromosomal abnormality in embryos is more common
• A parent known to carry a balanced translocation or other rearrangement
• Severe male factor infertility in selected cases

How the testing is done

• Genetic counselling first — before any cycle, a counsellor establishes what is being tested for and whether testing will actually answer your question.
• IVF with ICSI — ICSI is used so that no stray sperm contaminates the genetic sample.
• Blastocyst culture — embryos are grown to day five or six so that enough cells are available for a safe biopsy.
• Biopsy — a few cells are removed from the outer layer of each suitable blastocyst, the part that would become the placenta rather than the baby.
• Freezing — embryos are vitrified while results are awaited.
• Testing and reporting — the sample is analysed in our in-house genetics laboratory and the report is explained alongside a counsellor.
• Frozen transfer — a suitable embryo is transferred in a later, prepared cycle.

Honest limits of embryo testing

Embryo testing narrows risk. It does not remove it, and it is important to go in understanding that.

• A normal result is not a guarantee of implantation, pregnancy or a healthy baby.
• No test screens for every genetic condition — each test looks for what it was set up to look for.
• Biopsy carries a small risk to the embryo, and some results come back inconclusive and need repeating.
• Mosaic results, where the sample contains both normal and abnormal cells, can be genuinely difficult to interpret and need careful counselling.
• Some cycles produce no embryo suitable for biopsy, or no embryo that passes testing.

Embryo sex information and Sri Lankan guidance

Chromosomal testing reports sex chromosomes, so the information exists as a by-product of testing. What can be done with it is a separate question.

Sri Lankan ART professional guidance limits embryo sex selection to medically justified reasons, such as avoiding a serious sex-linked disorder, and asks centres to refrain from sex selection performed solely for family balancing or personal preference. We follow that guidance. Where you think a medical indication may apply, we are glad to review it with you.

Frequently asked questions