By Dr. Ram Prakash, Maaeri Fertility & IVF Centre
Do you know that PGT is not one test but three? Preimplantation genetic testing is a collective term which covers three quite distinct tests that can be performed on your embryos before a transfer in an IVF cycle. Each one of them addresses a different genetic question and each one has its own specific indications. Understanding which PGT testing type applies to your own situation, and understanding why it applies, is the difference between an add-on which genuinely changes your outcome and one which simply adds cost without any clinical benefit at all.
What Is Preimplantation Genetic Testing and When Is It Used?
PGT requires an embryo to reach the blastocyst stage, which is day 5 to 6, and at that point cells are removed from the outer layer, called the trophectoderm, so that they can be analysed. The embryo then goes into vitrification while the results are being processed, and typically that takes one to three weeks. Only the suitable embryos are used in a subsequent frozen transfer. All three of the types share this same process, and what differs between them is the genetic question which is being answered.
What Are the Three Types of PGT Testing?
PGT-A: Preimplantation Genetic Testing for Aneuploidies
PGT-A screens for chromosomal abnormalities, meaning whether an embryo has the correct number of chromosomes, which is 46 in humans. An aneuploid embryo cannot develop into a healthy pregnancy and it is the leading cause of both IVF failure and early miscarriage. Moreover, the proportion of aneuploid embryos increases substantially as maternal age goes up, and this is exactly why PGT-A is most commonly indicated for women over 37, or for those who have a history of recurrent implantation failure, or repeated pregnancy loss behind them.
The thing to note is that PGT-A does not screen for any specific diseases. It screens for chromosome number only. So an embryo which passes PGT-A is chromosomally normal but it may still be carrying single-gene conditions if those have not been tested for separately.
PGT-M: Preimplantation Genetic Testing for Monogenic Disorders
PGT-M tests for specific single-gene conditions which are already known and which one or both of the partners carry. It is used where a couple has a known genetic condition running in the family, such as cystic fibrosis, spinal muscular atrophy or SMA, sickle cell disease, the BRCA1/2 mutations which are linked to hereditary cancer, or Huntington’s disease, and where they want to avoid passing it on to their child.
Unlike PGT-A, PGT-M requires a bespoke probe which has been designed for that one specific gene variant, and this involves one to two months of preparation beforehand. PGT-M is available at Maaeri in coordination with specialist genetics laboratories, and it is recommended that genetic counselling happens before any PGT-M cycle begins.
PGT-SR: Preimplantation Genetic Testing for Structural Rearrangements
PGT-SR is used where one partner carries a chromosomal structural rearrangement, and most commonly that is a translocation, which is where segments of two chromosomes have been exchanged with each other. Carriers of translocations are typically perfectly healthy themselves, however they produce a high proportion of unbalanced embryos, and that is what leads to recurrent miscarriage or to repeated IVF failure. PGT-SR is what identifies which of the embryos carry a balanced arrangement that is compatible with a healthy pregnancy.
Recurrent pregnancy loss with no other identified cause behind it is the typical prompt for this, and our team investigates it through karyotyping both of the partners as a part of the standard workup.
How Do You Know Which Type You Need?
| PGT Type | What It Tests | Who Needs It |
| PGT-A | Chromosome number (aneuploidy) | Age ≥37, repeated implantation failure, recurrent loss |
| PGT-M | Specific single-gene disorder | Known inherited condition in family or carrier status confirmed |
| PGT-SR | Chromosomal structural rearrangement | Recurrent miscarriage, carrier of translocation |
The PGT testing cost varies depending on the type, and PGT-M is typically the more expensive one because of that bespoke probe preparation.
Frequently Asked Questions
Can PGT guarantee a healthy baby?
No it cannot. PGT significantly reduces the risk of the one specific genetic problem which is being tested for, but it does not screen for every possible genetic condition. A normal PGT result means that the embryo is free of the abnormality which was tested for, and not that it is free of all possible conditions.
Does PGT damage the embryo?
The trophectoderm biopsy technique which is used today has a very low rate of embryo damage when it is performed by an experienced embryologist. Success rates coming from biopsied blastocysts are comparable to those from unbiopsied embryos in the experienced centres.
Is PGT-A recommended for everyone doing IVF?
No, and the evidence does not support universal PGT-A use. Its clearest benefit is in the patients where the aneuploidy rate is expected to be high, meaning women who are over 37, those who have had repeated failure, or couples who have had recurrent loss.
Understanding which PGT testing type applies to your own situation is a conversation to have with your fertility specialist, and it should be informed by your age, by your history, and by any genetic factors which are already known. At Maaeri we guide that discussion right from the first consultation rather than from a general cost comparison.
This article is for general educational purposes and is not a substitute for personalised medical advice from your fertility specialist or embryologist.