Prospective parents are increasingly being presented with genetic tests marketed as a way to select for desirable traits in their children, such as height and intelligence. However, experts caution that these tests cannot deliver on their promises, offering minimal benefits while posing real risks to patients, offspring, and society. The core issue is that these tests attempt to predict complex traits influenced by thousands of genes, rather than focusing on single-gene inherited conditions like cystic fibrosis.
Which Tests Are Being Offered?
Traditional preimplantation genetic testing (PGT) screens IVF embryos for known genetic disorders caused by mutations in a single gene. The newer tests, however, generate “polygenic risk scores” for individual embryos, attempting to predict a predisposition to conditions like heart disease or Alzheimer’s, or even traits like IQ and height. Parents can then use these scores to choose which embryo to implant.
Several companies in the United States, including Nucleus Genomics, currently offer these services. Nucleus Genomics actively markets these tests, with advertising campaigns featuring the tagline “Have your best baby,” and offering screening for over 2,000 traits, including eye color, hair color, and even a predisposition to acne.
What Does the Research Show?
Recent research has cast serious doubt on the reliability and clinical utility of these polygenic risk scores. A study published in the journal Human Reproduction evaluated whether this technology is ready for clinical use, using the same framework applied to assess any medical screening test. The findings demonstrate that these predictions are extremely uncertain.
Predicting the risk of late-onset diseases is particularly problematic, as the outcomes won’t be known for decades. Mathematical modeling suggests that any benefits are likely to be small – perhaps a few IQ points or 1-3 centimeters in height. Researchers emphasize that these seemingly small differences may not be clinically relevant.
A key limitation is that polygenic risk scores are derived from studies of populations who lived in significantly different environments than those of today. Factors like diet, exposure to pollutants, and access to healthcare have changed dramatically, impacting how genes express themselves. These scores examine only genetic predisposition, ignoring the substantial influence of environmental factors.
For example, IQ is heavily influenced by early childhood education, nutrition, and socioeconomic factors. Selecting an embryo based solely on a marginally “better” genetic score for intelligence, while neglecting these proven influences, is unlikely to yield significant results.
the phenomenon of pleiotropy – where a single gene affects multiple traits – introduces additional complexity. Selecting for a trait like higher educational achievement might inadvertently increase the risk of other conditions, such as bipolar disorder.
Ethical and Regulatory Concerns
In Australia, current guidelines recommend preimplantation genetic testing only to avoid serious genetic conditions. Using polygenic risk scores to select for traits, rather than to prevent disease, is inconsistent with these guidelines and operates in a regulatory gray area. Despite this, prospective parents are increasingly sending samples or genetic information overseas for analysis.
The use of this technology also raises profound ethical concerns, echoing historical eugenics movements. Selecting embryos based on desired traits risks entrenching discrimination and exacerbating social inequalities. The potential for decision paralysis is also significant. Parents faced with polygenic risk scores for multiple embryos across numerous conditions and traits may struggle to make informed choices, leading to anxiety and uncertainty.
There is an added irony: couples undergoing IVF solely for polygenic risk score testing, rather than for fertility issues, may actually reduce their chances of having a healthy baby. IVF itself carries risks, such as an increased risk of high blood pressure in pregnancy and preterm delivery, and the embryo biopsy process may also affect pregnancy outcomes.
The Take-Home Message
The pursuit of a “best” child through genetic optimization is misguided. A child’s well-being is far more dependent on a loving family, good nutrition, education, and healthcare than on minor variations in their genetic code. Environmental factors have a far greater influence on development than genetic predispositions. Focusing on these proven influences is far more likely to lead to a thriving child than attempting to manipulate genetic traits with unproven and potentially harmful technologies.
