The Guardian has learned that couples who have had ECO in the UK are using an apparent loophole in the law to rank their embryos based on genetic IQ predictions. But what is polygenic screening and does it work?
What types of tests can be carried out on embryos in the UK?
Fertility treatments are strictly regulated, and tests performed on embryos are legally limited to a list of serious medical conditions. These include about 1,700 monogenic diseases, including Huntington's disease, cystic fibrosis and sickle cell disease. Clinics can also test for aneuploidy—when an embryo has extra or missing chromosomes—which reduces the chance of a successful pregnancy or can lead to genetic conditions. Polygenic screening, or PGT-P, which aims to produce predictive measures of health, height, IQ and other characteristics, is not approved.
Why did this gray area arise?
As genetic sequencing has become faster and cheaper, laboratories typically test for aneuploidy (known as PGT-A testing) by generating a low-resolution genome sequence for each embryo. This sequence is not shared with IVF clinics – they only receive information about whether the embryo has missing or extra chromosomes. But patients have the right to access their medical data, including embryo information, under the GDPR and the Data Protection Act 2018.
What can this data tell us about the embryo?
This sequence will determine the sex of the embryo. When combined with high-quality parental genome sequences, it can also be used to predict mental and physical traits. Several US companies offer commercial health and IQ prediction services.
What is polygenic screening and does it work?
Traits such as height and intelligence are known to be partly inherited. But unlike a monogenic disease, the genetic component involves thousands of genes that vary between individuals and interact in complex ways with each other and with the environment.
However, by analyzing large genetic databases, scientists have developed algorithms that can predict a variety of physical and mental characteristics. These estimates are probabilistic: an embryo with a high predicted risk of developing diabetes is not guaranteed to develop the disease.
Proponents of polygenic screening say parents have the ability to make judgments about the technology's potential health benefits. However, others say the accuracy of the predictions has not been tested in the context of embryo selection and their use is not justified from a health perspective.
“Polygenic estimates tend to be very crude and reflect only a small part of the heritable component of complex traits such as IQ,” said Professor Frances Flinter from Guy's and St Thomas' NHS Foundation Trust and a member of the fertility regulator HFEA. “The main concern for geneticists is that the use of PGT-P represents a premature application of under-validated tests.”
