Pre-Implantation Genetic Testing (PGT) isn’t a new science, it’s been available to fertility specialists for some time now, but last year a great step forward was made by the laboratory that Reproductive Health Group work with that enables couples to make informed decisions about their journey to parenthood.
‘In the very simplest terms, PGT gives information about embryos’ genetic health to help embryologists select the best embryo for transfer and improve the chance of achieving a successful pregnancy. Once a known healthy embryo has implanted there is a higher likelihood of the pregnancy progressing to full term.
‘We use PGTai and recommend it for our older ladies and those who have had previous unsuccessful fertility treatment. This is because as we age, it has an effect on the genetic make-up of any embryos we make, either naturally or after IVF. When an embryo is created it should have 46 chromosomes; this is known as a ‘euploid’ embryo. If it hasn’t got 46 chromosomes then it is known as ‘aneuploid’ and is genetically abnormal. In older women, we see an increase in the number of Aneuploid embryos being created. When this happens, there is a vastly increased likelihood that the body will reject the embryo, resulting in no pregnancy or a miscarriage.
‘In PGTai, we take an embryo when it is at the blastocyst stage, just five days into its development. At this point, it has a central mass of differentiated cells that would go on to form the baby, and a surrounding cell mass that would go on to form the placenta – it is from here that we extract three to five cells for testing and send them to our chosen partners who are at the forefront of this type of technology. The ‘ai’ bit refers to the artificial intelligence element of the tests, which produce quite extraordinarily detailed results. The AI is based on the test results of 1,000 embryos that went on to create healthy babies and the whole testing platform has been validated on 10,000 embryo tests and 5 million data points.
‘Until fairly recently, the results we would receive back from testing would tell us if the embryo was Euploid or Aneuploid. We would have many patients for whom all the embryos we tested were recorded as Aneuploid, meaning that we couldn’t proceed with treatment with those embryos. Now, the AI is so smart, it can in effect give us a sliding scale of ‘normality’.
‘Today, we have four bands. euploid; low level mosaic – meaning that the embryo has 20-40% of its cells showing as ‘abnormal’; high level mosaic – with 40-80% of the cells as abnormal; and finally, aneuploid.
So that’s the science, but what does this mean for patients?
‘As an example, we might have a patient with two day-5 blastocysts which both have cells sent for PGTai. The results for one blastocyst comes back as aneuploid (abnormal and cannot be used for treatment) and the other embryo comes back as a low level mosaic, which can be used for treatment: implanting a low level mosaic embryo in the womb can result in a positive pregnancy test and recent evidence has shown that these pregnancies give a 50% chance of delivery of a live baby. Previously we would have rejected both of these embryos. A high level mosaic rating offers a 30% chance of a successful pregnancy.
‘It’s really about giving couples more opportunity to decide how they want to proceed. Everybody who has embryos sent for genetic testing from RHG has the opportunity to participate in genetic counselling, where we can help them understand the science and what that means for them, personally.
‘For me, it’s very exciting. I honestly believe that this form of testing will become available for all women and that there will come a time when it will become routine for embryos to be tested before they are used for treatment. This is ground breaking technology that has improved the accuracy with interpreting the results from PGT and removed any subjectivity. This is a very exciting area of reproductive science and it’s wonderful to be at the forefront of it in the UK.’