How much would you pay for a smarter baby?

The burden of perfection

Now startups are adding a third screen: PGT-P, which scores embryos for conditions and traits determined by multiple genes, potentially ranging from certain cancers to eye colour and IQ. Demand for such tests could be substantial. A survey published in 2023 in Science found that 43% of all IVF participants would use polygenic screening to increase their child's chance of getting into an elite university, provided it were safe and free. One third said the same for genetic editing.

Consider Arthur Zey, a tech worker, and his husband Chase Popp, a teacher. Mr Zey says he has always been a "tech nerd" and wanted to apply his skills to the process of having a child. "Most of my professional career I've been a product manager in tech, and so in some ways this is just like another product to manage," he says. Earlier this year, the couple had a son using an embryo selected from a group of six on the basis of the results of polygenic screening provided by Herasight. That allowed them to see risk scores for monogenic diseases and more than a dozen polygenic diseases. The startup also gave them predicted ranges for IQ and height.

Messrs Zey and Popp say they hoped to maximise their son's lifespan, rather than his height or IQ. Yet Mr Zey knows there are advantages to being tall and smart. "All I could do is look at the results for my six embryos and say: 'Okay, it kind of seems like this one is better.'"

For now, Messrs Zey and Popp are unusual. Commercial PGT-P screening is a niche industry. Startups like Herasight cater to a small population of typically very rich people, mostly in America. Even so, that has not stopped them from drawing plenty of criticism.

Some concerns the underlying science. Polygenic risk scores are based on genome-wide association studies (GWAS), which use data from large populations to try to discern associations between genetic variants and specific conditions and traits. Companies that offer screening claim that comparing embryos' genomes to risk scores derived from these databases, sometimes with adjustments based on ancestry and family history, allows them to come up with individual assessments.

That is disputed, however. Although selecting on the basis of polygenic risk scores works across many offspring, as in animal breeding, it is less sure to have the desired result for a single child, notes Kevin Mitchell of Trinity College Dublin.

Herasight attempts to deal with this issue by validating its risk scores using sibling data from GWAS datasets to ensure its models retain predictive value within a single family. It claims that, if it tests ten embryos for a couple where both parents have type-2 diabetes, it can reduce their child's absolute risk of developing the condition by 12-20 percentage points, from a baseline of 40-60%.

Some argue that the magnitude of the benefits from embryo screening are overstated. If parents picked from ten viable embryos, the median boost to their child's height would be 2.9cm, according to a paper in Cell in 2019, based on technology at the time. If they selected for IQ, the gain would be three points—unlikely to be life-changing. Moreover, for those picking among fewer than five embryos, the expected gains drop precipitously. Dagan Wells of the University of Oxford adds that, for many conditions, genes are less important than environmental factors such as diet.

Selecting against some traits could also have unintended consequences. Genetic material can have different effects in different parts of the body, a phenomenon called pleiotropy. If parents select an embryo intending to lower their child's risk of a certain disease, they may be neglecting or exacerbating problems for which providers do not (or cannot) offer a score.

Yet many of the technical issues, not least the lack of training data among certain populations, should improve with time. The Cell paper estimated that increasing the sample size of the underlying databases could double the median gain in IQ points from polygenic scoring. With pleiotropy, some studies suggest that most genetic correlations between pairs of polygenic diseases are either positive—meaning cutting the chance of one decreases the chance of others—or insignificant. At present, the technology is "kind of a promissory note", says Trinity's Dr Mitchell. "They say, 'Trust us, this is a bit shit right now, but it'll be good soon'."

If technological problems are resolved, ethical ones will grow. Some opponents are concerned that screening startups are promoting a friendlier version of eugenics. Others worry that embryo editing—on which America has applied a de facto ban since 2016—could come next.

Industry insiders reject the fretting, sometimes bluntly. Risk scores may not be perfect, but they are "best in class", says Delian Asparouhov of Founders Fund, a VC firm co-founded by Mr Thiel, which has invested in various fertility startups.

"What I hate about some of the traditional health-care industry and genetic counsellors is they're like, 'You need to have a Harvard clinical-grade licence'" to interpret genetic data. "F*** that," he continues. "I just want whatever the best statistical models are. I don't need a PhD to read this stuff." (Herasight, Nucleus and Orchid all have genetic counsellors to walk clients through their results.) As for ethics, Mr Asparouhov argues that all parents-to-be engage in a form of genetic selection when they choose a partner. "If this is eugenics, then so is Hinge," he argues.

Most of the companies offering PGT-P are more circumspect. They say their customers are mainly looking for ways to ensure their children are healthy, rather than to create "super-babies". Yet their decision to offer scores for intelligence and aesthetic traits suggests they recognise there is a market for the latter.

Arguments over the future of a small cohort of startups may seem like a niche concern. But if IVF gets cheaper and genetic data more abundant, as looks likely, the business of embryo screening will only grow—along with the ferocity of the debate. The nearly 50-year history of the fertility industry is full of technologies that were once considered contentious, including IVF. Startups such as Nucleus, Orchid and Herasight are, in that sense, at least nothing new.