Scientists from Oxford University and partner institutions have found that prospective parents select embryos based on genetic predictions of intelligence and behavior when given the option, despite initially expressing a preference for medical screening only.
The study, published in the journal Nature Human Behaviour, examined the choices of more than 2,000 adults across the United States and China during hypothetical in vitro fertilisation procedures.
In vitro fertilisation, a medical procedure where eggs are fertilised by sperm outside the body before transfer to the uterus, increasingly incorporates polygenic genetic testing. These tests analyse thousands of genetic variants to calculate likelihood scores for complex health conditions and physical traits.
Researchers found a sharp contradiction between what people say they want to know prior to testing and how they act when presented with genetic profiles of embryos.
Testing Preferences Versus Real Choices
In the United States, researchers surveyed 1,467 adults chosen to reflect the national population. A subgroup of 735 participants was asked whether they would agree to perform genetic testing on embryos for four specific conditions and traits.
Screening for heart disease received the highest support at 79 percent, followed by low intelligence quotient at 65 percent, antisocial behaviour at 58 percent, and visual impairment at 55 percent. The initial survey suggested a strong public preference for medical screening over non-medical traits.
However, when a second group of 732 American participants was presented with genetic profiles of embryo pairs and asked to choose between them, the distinction between medical conditions and behavioral traits largely disappeared.
An embryo with a higher than average risk of heart disease was 40 percentage points less likely to be selected compared to one with average risk. Antisocial behaviour reduced the likelihood of selection by 36 percentage points, while a low intelligence quotient reduced it by 32 percentage points.
By contrast, visual impairment, which is a recognized medical condition, reduced an embryo's selection probability by only 19 percentage points, making it less of a deterrent than non-medical traits like low intelligence or antisocial behaviour.
Deliberate Ignorance and Chinese Study Findings
A parallel experiment conducted with 623 adults in China demonstrated a similar decision pattern, with behavioral traits and cognitive scores heavily influencing choices, although the observed differences were slightly larger.
The study authors described this pattern of behaviour as deliberate ignorance. They explained that individuals often prefer not to request non-medical genetic information beforehand to avoid uncomfortable moral decisions, but remain unable to ignore the data once it is placed in front of them.
Edmond Awad, the lead author of the study, said that choosing not to look is not the same as not caring about the outcome. He noted that people do not think in rigid categories when faced with a concrete choice between two embryos.
Awad emphasised that the findings have major implications for informed consent protocols in fertility clinics. He suggested that prospective parents should reflect not on what they initially wish to know, but on what specific genetic information would actually dictate their final decision.
Limitations of Polygenic Embryo Scores
Polygenic embryo screening is already offered by commercial companies to assess risks for common adult conditions such as heart disease and diabetes, alongside predictions for physical traits such as height and cognitive capacity.
However, the research team warned that a genetic score is not a crystal ball. Cognitive ability and behavioral traits depend on thousands of genetic variants interacting with education, nutrition, family environment, health, and social circumstances.
The researchers noted that the capacity to accurately predict traits like intelligence quotient is far more limited when comparing embryos from the same parents. They cautioned that real-world benefits of selecting embryos based on polygenic trait scores are much smaller than the simplified scenarios presented in the experiment.
The team added that a specific genetic score does not mean an embryo is destined to develop antisocial behaviour, nor does it guarantee that another embryo will grow into a person with superior intellectual capability.
Regulatory Frameworks and Next Steps
The research was conducted by scientists from Oxford University, Exeter University, and the National University of Singapore, alongside other international institutions.
Existing regulatory frameworks in many countries establish a strict division between embryo selection for preventing medical diseases and selection based on non-medical traits. The study authors concluded that this legal boundary does not align with how prospective parents actually value genetic information when making reproductive choices.
