Pre-Implantation Genetic Testing For Monogenic Diseases (PGT-M) and Structural Arrangements (PGT-SR) detect specific genetic diseases and chromosomal abnormalities in embryos. It is recommended for certain patient groups to improve the chances of a successful healthy pregnancy.
What is PGT-M / PGT-SR?

What is PGT-M / PGT-SR?

Who is it recommended for?

  • Couples where one or both partner(s) is a known carrier of a balanced chromosomal structural rearrangement (translocation).
  • Couples where one or both partner(s) is a known carrier of a serious genetic condition.
  • Women or couples who have experienced recurring miscarriages.
  • Women or couples who have experienced recurring implantation failure after several attempts with IVF.
  • Men or couples with abnormalities in spermatozoa meiosis.
  • Women of advanced maternal age (>35 years).

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What is the difference between PGT-A and PGT-SR?

PGT-M is suitable for couples where one or both partner(s) are carriers of a known monogenic disease, or have a serious condition themselves, and are concerned about transmitting this condition to their baby. While the most common include cystic fibrosis and sickle cell anaemia, PGT-M can also be used to identify genetic conditions that are more rare. There is a list of conditions for which PGT-M is approved and it is regulated by the Human Fertilisation & Embryology Authority (HFEA). During PGT-M, molecular diagnosis is used to confirm whether an embryo will be affected by a specific disease.

PGT-SR is suitable for carriers of chromosomal abnormalities (translocations). Although it’s estimated that 1 in every 500 people is a carrier of a translocation, carriers are normally healthy and often unaware until they try to have children. Being a carrier means there is a higher risk of producing abnormal embryos, which can make it difficult to conceive. Through PGT-SR, cytogenetic molecular diagnosis allows normal or balanced embryos to be identified by their chromosomal arrangements.


The purpose of PGT is to analyse embryos following in vitro fertilisation (IVF) to assess and identify the healthiest embryos which are free of any potentially harmful abnormalities. The procedure takes place before they are transferred to the uterus, prior to pregnancy. A biopsy is performed using a tiny sample of cells extracted from the trophectoderm (the cells which will go on to form the placenta), so it does not cause any harm to the embryo. By using micromanipulation and cytogenetic molecular diagnosis techniques, we are able to analyse the cells and distinguish which embryos are unaffected. This allows us to carefully select an embryo for transfer that is most likely to implant and improves the chances of having a healthy baby.

  1. Preliminary phase. In this initial phase, genetic characterisation tests are carried out on the prospective parents for specific conditions, with the objective of gaining as much information as possible prior to applying PGT.
  2. Obtaining embryos. This involves producing the embryos through the process of “in vitro” assisted reproduction methods, even if the prospective parents are not afflicted by any fertility problems.
  3. Embryo biopsy. This consists of extracting a tiny sample of cells from the embryo without compromising its embryonic development. Once the biopsy has been performed, the embryos are put back into the incubator where they stay until the results of the diagnosis are obtained and their viability for transfer is assessed.
  4. Genetic diagnosis and embryo transfer. The cells are processed for analysis and an examination is carried out. Using the results of the analysis, the medical team support the couple as they decide their next steps in which an embryo will be transferred.

What are chromosomes and genes?

There are millions of cells in the human body. In every cell, there is a nucleus containing 46 chromosomes consisting of 23 pairs (23 from paternal sperm and 23 from the maternal egg). Chromosomes are the structures which carry our genes. Genes are made up of tiny fragments of deoxyribonucleic acid, known as DNA, which contain our unique genetic code. They provide instructions which control the way a human body and its characteristics grow and develop.

Which chromosomal abnormalities can cause diseases?

  • A numerical alteration: This is an anomaly that affects the number of copies there are of a chromosome. For example, having an extra or missing chromosome instead of a pair. The most common example is Down’s syndrome, in which there are three copies of chromosome 21.
  • A structural alteration: This is an anomaly in the structure of a chromosome in which a section is missing, out of place or duplicated.
  • A monogenic disease: This is a genetic disorder caused by a fault or mutation in a single gene. Known examples of monogenic diseases include Cystic Fibrosis, Haemophilia, Fragile X Syndrome, Myotonic Dystrophy and Huntington’s Disease.

List of monogenic diseases

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