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Preimplantation Genetic Testing (PGT)

Preimplantation Genetic Testing (PGT)

Having a healthy baby is something all parents hope for. But, what if you could go even further than that? What if you could help ensure the health of not only your child, but your grandchildren and many generations to follow?

Preimplantation Genetic Testing (PGT) formerly known as Preimplantation Genetic Diagnosis (PGD) and Preimplantation Genetic Screening (PGS) is used primarily to identify genetic defects in embryos created through In Vitro Fertilisation (IVF) before transferring them to the womb (uterus), thus decreasing pregnancy miscarriages caused by chromosomal abnormalities, implantation failures and births with genetic abnormalities.

It is important to note that the new term PGT doesn’t change the way embryos have been tested with PGD or PGS, it is just a terminology now used to describe all genetic tests.

The process requires In Vitro Fertilisation (IVF) to obtain a number of oocytes and embryos for evaluation. Studies have shown that PGT cycles are most successful when implemented on 8 or more blastocyst embryos with at least 5 good quality ones. The process involves removing cells (trophectoderm) not destined to form the baby from a day 5 (blastocyst) (trophectoderm biopsy) and the cells which are a representative of the embryo, are sent for genetic analysis.

Preimplantation Genetic Testing provides parents with the option of detecting potential defects in an embryo before transfer. The genetic tests are performed on the cells biopsied from day 5 embryos prior to implantation and pregnancy. The rest of the embryos remain in the embryology laboratory. This offers specialists the opportunity to examine far beyond the superficial appearance of an embryo during an IVF treatment.

At Bridge Clinic, PGT is an important treatment option for couples who are undergoing IVF treatment either for fertility reasons or for the option of having their embryos thoroughly examined for specific gene mutations or chromosomal abnormalities.

There are 3 types of Preimplantation Genetic Testing (PGT);

  • PGT-M
  • PGT-A
  • PGT-SR

PGT-M (PGT- Monogenic/Single Gene Disorders) formerly known as Preimplantation Genetic Diagnosis (PGD) is a sophisticated reproductive technology used in conjunction with IVF treatment to test early embryos for specific or single gene disorders. This treatment is important for couples that have a history of genetic disease which can be passed down to the child e.g., sickle cell anaemia, cystic fibrosis, beta-thalassemia etc.

PGT-A (PGT-“Aneuploidy”) formerly known as PGS is now used to describe screening embryos for sporadic chromosome abnormalities. The process is used to test embryos by counting the 46 chromosomes in order to detect an additional or missing chromosome(s) (“aneuploidy”). Normal embryos are usually the most likely to implant and result in a successful pregnancy. The screening helps to reduce the chance of having a child with extra or missing chromosomes, such as; Down syndrome, Turners syndrome, Patau’s syndrome, Edward’s syndrome, abnormal sperm parameters etc.

PGT-SR (PGT-“Structural Rearrangements”) formerly known as PGD for chromosomal translocations (balanced or unbalanced) or inversions is used to test embryos for chromosomal abnormalities as well as abnormal chromosomal positions and rearrangements. It is recommended for couples with recurrent pregnancy loss as well as a history of recurrent failed IVF/implantation and for couples whose female partners are 35 years and above.

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

PGT-M (PGD) is often confused with PGT-A (PGS), however the two processes are implemented to establish entirely different results. PGT-M as described, tests for specific genetic conditions, whereas PGT-A tests are for overall chromosomal normalcy in embryos. In other words, PGT-M is ideal for prospective parents who have a specific genetic condition they do not want to pass on to their offspring.

Benefits of PGT-A

  • It can be used to test for more than 100 specific genetic conditions
  • Miscarriage rates following PGT for chromosomal screening are far less than with standard IVF
  • Since the procedure is performed before implantation, couples may feel more comfortable with deciding whether to go ahead with the embryo transfer or not, should results not be favourable
  • The procedure enables couples who may be at risk of passing genetic conditions to their children, the opportunity of pursuing biological parenthood, which they may not have done otherwise
  • Offers the option of family balancing and gender selection
  • It is also useful for eliminating sex-linked hereditary diseases
  • Women over the age of 35 years
  • Women who have experienced recurrent miscarriages
  • Severe male factor infertility

Who can benefit from PGT-M (PGD)?

  • Carriers of single gene disorders
  • Couples with specific chromosomal disorders in their family history
  • Couples that are carriers of sex-linked genetic disorders
  • Parents who have a child with a serious genetic condition, but want to get pregnant again

Who can benefit from PGT-SR (PGD for chromosomes translocations)?

  • Women over the age of 35 years
  • Women who have experienced recurrent pregnancy loss
  • Women who have experienced repeated IVF and implantation failures
  • Couples with history of chromosomal balanced and/or unbalanced translocations or inversions

Human Leukocyte Antigen (HLA) Matching and PGT-M

  • HLA are proteins or markers found on most cells in your body.
  • Your immune system uses these markers to recognise which cells belong in your body and which do not.
  • It is used to match patients and donors for bone marrow or cord blood transplants.
  • A close match between a donor’s and a patient’s HLA markers is essential for a successful transplant outcome.
  • HLA matching promotes the growth and development of new healthy blood cells and reduces the risk of a post-transplant complication.
  • PGT-M can be offered with HLA matching/typing if there is an affected child that will need a transplant of cells in the future.
  • It is important that more embryos are generated for this process to increase the chances of a match.

PGT at Bridge Clinic

In an effort to stay abreast of international medical innovation, Bridge Clinic offers all the types of PGT as a specialised service forming part of our Advanced Care. Our affiliation with IVF Centres Prof. Zech in Austria and reputable genetic institutions, ensures that our physicians are fully trained internationally and remain at the cutting edge of new technology and procedures in the field of genetics.

Speak to a specialist today.
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Visit any of our clinics in Lagos, Abuja or Port Harcourt or call the customer care line on 0201 631 0092.

Learn more about PGT here

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