Understanding embryo testing
Following the revelation by the Human Fertilisation and Embryology Authority (HFEA) earlier this year that at least one so-called ‘three parent baby’ had been born in the UK, the debate about ‘designer babies’ rumbles on, and a specialist fertility consultant at Bristol Centre for Reproductive Medicine (BCRM) has said she is concerned by public perception about the difference between the contentious practice of gene editing and the relatively uncontroversial process of healthy embryo selection.
BCRM’s medical director, Amanda Jefferys, said: “Reproductive science is the science of creating life and providing solutions to infertility, and it is the responsibility of those who work in the field to help create the healthiest babies possible.
“One of the ways we achieve this is to analyse a batch of embryos we’ve created using in-vitro fertilisation and to select the healthiest embryo for implantation in the mother’s womb – which is exactly what’s been happening since the birth of the first IVF baby, Louise Brown, 45 years ago, except that it’s become more sophisticated since then.
“Preimplantation Genetic Testing (PGT) is conducted in around 5% of IVF cycles in the UK under licence from the fertility regulator, the HFEA, and is generally undertaken on five-day-old embryos.
“PGT cannot be used for sex selection purposes. Sex selection is illegal in the UK.
“We can test various aspects of the genetic makeup of the embryo using a technique known as preimplantation genetic testing (PGT), of which there are three types: PGT-M, PGT-A and PGT-SR.”
“One option is PGT-M which offers those would-be parents who are aware they carry genes for specific inherited diseases a way of identifying embryos which do not carry those problematic genes.
“This can almost rule out the chances of a baby being born with one of around 250 debilitating or life-limiting conditions such as thalassemia, early-onset Alzheimer’s and cystic fibrosis.
“There is also the option of a screening test known as PGT-A which checks whether the embryo carries a normal number of chromosomes.
“This is available to anyone undergoing IVF, although it’s most likely to benefit those couples that have a greater likelihood of having a chromosome problem in their embryos because of age, also couples with a history of recurrent miscarriage, those who have had several failed IVF attempts, or couples who have had previous pregnancies affected by chromosome abnormalities.
“Alternatively, if initial investigations have indicated it might be beneficial to check for structural rearrangements in the chromosomes within the embryo - which may increase the risk or miscarriage or inherited abnormalities – PGT-SR would be the most appropriate test.
“So, essentially, preimplantation genetic testing is a selection tool to increase the likelihood of a healthy on-going pregnancy. It is not a guarantee of pregnancy, but we know that chromosomally normal embryos are more likely to result in a successful pregnancy and live birth, and that is very much what we are in the business of helping with.”
BCRM www.fertilitybristol.com is the longest established fertility clinic in Bristol, helping people from throughout the South West and Wales with fertility treatment for both private and NHS patients. The clinic is involved in innovative research and has one of the best success rates with IVF and other fertility treatments in the UK.
