Testing for a limited number of serious conditions involving single genes is permitted in the UK through preimplantation genetic diagnosis (PGD). However, traits such as intelligence are much more complex.
As intelligence is affected by a huge number of genes, the test involves analysing many regions of DNA at once in order to assess for risks of certain conditions or traits. The result is known as a polygenic risk score. The same approach is used at present in tests assessing risk of heart disease, breast cancer, and diabetes.
'Chromosomal abnormalities are already evaluated,' Dr Nathan Treff, chief scientific officer of Genomic Prediction, the company that developed the test, told the New Scientist. 'For complex disorders though we have to evaluate the entire genome in order to get the risk. The very extreme end of risk, the opposite of intellectual ability, is intellectual disability. There is a potential to avoid that condition by selecting an embryo that does not have it.'
Stephen Hsu, co-founder of Genomic Prediction, added: 'I think people are going to demand that. If we don't do it, some other company will.'
The polygenic risk score cannot predict future IQ for an embryo, but it can identify genetic outliers – embryos with an increased chance of having an IQ 25 points below average. The screening test will be for likelihood of 'mental disability', the firm said, but in future it could be used to identify embryos that are more likely to develop high intelligence. The test will not be used to aid parents in choosing high IQ embryos, because of ethical concerns, Genomic Prediction said.
The test's potential is constrained by the fact that people using IVF will have just a few embryos to choose from. As the selection of embryos all come from the same biological parents, the range of polygenic scores is unlikely to be very wide.
Professor Peter Visscher, a geneticist at the University of Queensland, expressed concern at the screening test. 'You don't know what you're selecting for and what comes with it, but there are people who pay hundreds of thousands of dollars to have their dead pet cloned. I'm sure there are people who would do this.'
Dr Ewan Birney, director of the European Bioinformatics Institute, told the Times that he had concerns about the potential consequences of this form of selection, as not enough is known about the genetics of inheritance.
Offering such a test would be illegal in the UK. Embryos may be screened for chromosomal abnormalities, such as Down's syndrome, and single-gene tests are permitted only for an approved list of serious conditions, regulated by the Human Fertilisation and Embryology Authority (HFEA). US clinics are less regulated and can offer a wider variety of tests, including sex selection.
Dr Simon Fishel, president of Care fertility clinics, told The Times that he would like to see the HFEA consider licensing these tests: 'Cognitive disability is a health issue,' he said. 'It's always about balancing the good versus the potential for bad. We had this argument when PGD (preimplantation genetic diagnosis) was originally introduced. Without a shadow of a doubt it's been lifesaving.'