Pre-implantation genetic testing (PGT)


Genetic tests to check chromosomes in an embryo for abnormalities such as monogenic disorders, structural rearrangements and aneuploidy.

Lister Fertility Clinic at The Portland Hospital _ 0522_050

Preimplantation genetic testing for structural rearrangements (PGT-SR)

You or your partner have been diagnosed as having an abnormal karyotype (the number and arrangement of the chromosomes within the cells). Either a robertsonian or reciprocal translocation may have been diagnosed, or an inversion may have been detected. The presence of this re-arrangement will potentially make it difficult to conceive a healthy pregnancy naturally, and may have already resulted in implantation failure or recurrent miscarriage.

Next generation sequencing (NGS) is the most well-established of the available methods for PGT-SR. It allows us to comprehensively screen embryos for abnormalities in all 23 chromosomes before transfer. 95% of structural rearrangements can be detected by NGS and the embryologist will be able to confirm the exact testing effectiveness with your particular karyotype by consulting with Juno Genetics on your behalf.

The process for PGT-SR is the same as standard PGT apart from it is recommended that all PGT-SR cases use ICSI as the method of fertilisation to ensure that there is no extra risk of DNA contamination, that could make the results unreliable. It is also mandatory that all couples embarking on IVF treatment for testing with a known structural rearrangement have consulted a Genetic Counsellor prior to commencement.

No test is 100% accurate, so following any genetic screening we recommend that patients who become pregnant undergo prenatal screening if deemed appropriate by their obstetric team.

Preimplantation genetic testing for monogenic disorders (PGT-M)

A single gene disorder is the result of a single variant (mutated) gene and there are estimated to be over 4000 human conditions caused by single gene defects. Examples of these are Huntington's disease, neurofibromatosis, cystic fibrosis and sickle-cell anaemia. You or your partner, or both of you, may have been made aware that you carry a variant gene that could lead to a child inheriting a genetic condition.

PGT-M is a method of testing embryos produced during an IVF treatment cycle for particular genetic disorders before they are transferred to the uterus and is now available for virtually all single gene disorders. The aim of PGT-M is to provide couples at high-risk of passing on an inherited disorder to their children with an improved chance of having an unaffected pregnancy. PGT-M dramatically reduces the likelihood that an affected fetus will be detected during prenatal testing and therefore decreases the probability that parents will face the difficult decision of whether or not to terminate a pregnancy.

Who might benefit from PGT-M?

Any couples who know they are carriers of a serious inherited condition may be interested in PGT-M. Many of those who request PGT-M are fertile and undergo IVF for the sole reason that they wish to avoid an affected pregnancy which may require the possibility of termination.

Confirmation and Licensing
As long as a genetic disease has an identified variant, PGT-M should be possible. Following appropriate genetic counselling and in conjunction with the scientific team at Juno Genetics, we will determine if PGT-M with karyomapping can be done and that the HFEA has licensed the testing of this condition. An HFEA license has to be in place for each condition. It may be necessary to apply for a license for your particular condition and this process can take up to 16 weeks.

The Process and the Work Up
PGT-M is achieved through a process called Karyomapping. The preparation for PGT-M with Karyomapping involves the design of a specific custom-made test and mapping platform for each couple. This will then be used to detect the embryos that are affected with the genetic condition being tested for. For this test plan to be designed Juno Genetics will require blood samples or buccal cells from the couple and potentially other affected family members. The time required for preliminary testing is extremely variable but takes approximately 6 weeks to be made ready for use.

Stimulation and Embryo Biopsy
The ovaries are stimulated and eggs are collected and then fertilised using intracytoplasmic sperm injection (ICSI). The use of ICSI reduces the risk of DNA contamination derived from sperm. Embryos will be cultured to the blastocyst stage on day 5 or day 6 where 5-10 cells can then safely be taken from the embryo. The cells are placed in test-tubes and sent to the genetics laboratory by courier. The tested embryos do not leave the IVF clinic, they are immediately cryopreserved (frozen) until test results are available.

Genetic testing
The cells are each analysed independently using the patient specific karyomapping method. The karyomapping method will also comprehensively screen for abnormalities in all 24 chromosomes. We can then choose appropriate embryos for transfer based on these genetic results.

No screening test is 100% accurate, so following any genetic screening we recommend that patients who become pregnant, undergo prenatal testing which will reveal whether the genetic diagnosis was correct, and confirm whether or not the foetus is unaffected by the specific disease or mutation.

Please contact the embryologists in the IVF lab to discuss any further specific needs you may have.

PGT-A (Aneuploidy)

Preimplantation genetic testing (PGT)

Next generation sequencing (NGS) is the most well-established of the available methods for pre-implantation genetic testing (PGT). It allows us to comprehensively screen embryos for abnormalities in all 24 chromosomes before transfer. Genetically normal embryos have a higher chance of implantation and the resulting pregnancies have a lower chance of miscarriage. Testing embryos by NGS may therefore increase the likelihood of pregnancy, reduce the chances of a pregnancy loss, and improve the odds of a live birth outcome. Standard PGT is termed preimplantation genetic testing for aneuploidies (PGT-A). This covers the majority of requirements for patients looking to reduce the chance of miscarriage or infertility often associated with advanced maternal age.

Assisted Reproduction

Initially an IVF cycle using PGT-A begins in the same way as any other, with the stimulation of the ovaries to produce eggs, followed by their collection and fertilisation. The embryos will then remain in culture in the laboratory for 5-6 days.

Embryo Biopsy

When the developing embryos are five or six days old and have reached the blastocyst stage a few cells are removed from each blastocyst by our highly trained biopsy practitioners and taken for testing.

The cells are placed in special test-tubes and sent by courier to the Juno laboratory in Oxford. The tested embryos are then immediately cryopreserved (frozen) at the Lister fertility clinic until the test results are available.

Genetic testing

The cells are each analysed independently by NGS and the test results indicate how many copies there are of each chromosome, revealing any abnormal embryos. Results are available to us within 2 weeks. Once we have the results they will be shared with the patient and if any of the embryos are suitable they can be returned to the patient during a frozen embryo replacement cycle (FET).

No test is 100% accurate, so following any genetic screening we recommend that patients who become pregnant undergo prenatal screening if deemed appropriate by the obstetric team.

We have chosen to partner with Juno Genetics for the genetic screening of embryos. The Juno team have an international reputation as pioneers in the field of reproductive genetics. When it comes to the genetic testing of embryos, it would be difficult, if not impossible, to find a more experienced and respected group anywhere in the world. Juno Genetics prioritises safety and accuracy, and has the highest level of laboratory accreditation available. The tests it offers have undergone extensive validation in order to confirm their reliability. Juno Genetics also offers extensive support, including a comprehensive genetic counselling service, and is always willing to go the extra mile to deliver accurate tests. The innovative genetic services offered by Juno Genetics are at the cutting edge of technology, and evidence suggests that their tests are more accurate than others currently available. Juno Genetics was originally established in the UK, but now has additional laboratories in Spain and the USA. Its UK staff have more than 150 years of combined experience providing genetic tests related to infertility, IVF and pregnancy, and lead the field, having published more than 200 scientific papers.

If you have a specific chromosome rearrangement that needs testing (translocation or inversion) please see the PGT-SR information.

If you have a specific single gene mutation that needs testing for please see the PGT-M information.

What is Preimplantation Genetic Screening?

Emma Whitney, Senior Embryologist at the Lister Fertility Clinic explains what preimplantation genetic screening does and how the process works. 

Our Pre-implantation genetic testing (PGT) locations

Lister Fertility Clinic at The Portland Hospital

Lister Fertility Clinic at The Portland Hospital

215 Great Portland Street W1W 5PN London
Lister Fertility Clinic

Lister Fertility Clinic

Chelsea Bridge Road SW1W 8RH London

This content is intended for general information only and does not replace the need for personal advice from a qualified health professional.