Edited 2/2/09: The cited study discusses pre-natal genetic screening, not only embryo screening; I’ve updated some wording to reflect this, but it doesn’t have any major impact on the overall message.
Razib points to an article suggesting that Australian couples are “flocking” to a US fertility clinic that allows them to screen their potential IVF embryos for sex and even cosmetic traits like skin and eye colour, in addition to variants that predispose to severe disease risk. (“Flocking”, in this context, means about 14 couples a month.)
This follows on the heels of a fairly widely-publicised study published last week that surveyed around 1,000 genetic counselling patients about their attitudes towards pre-natal genetic testing. The study was sold to the media as indicating that “consumers desire more genetic testing, but not designer babies” – but the numbers actually suggest a substantial market for genetic screening.
The survey found that the majority of respondents would elect to screen for diseases like mental retardation, blindness, cancer and heart disease, and a hefty minority (20%) would screen for a disease that would result in death by the age of 50. More surprisingly, over 10% of respondents would screen for tall stature, athletic performance, or increased intelligence. Although this population is not a perfectly representative sample of the broader population, I’m still surprised to see that demand for such a socially unacceptable process is as high as this.
No doubt stories like this will result in increased hand-wringing and predictions of moral anarchy from social conservatives over the next few years. However, there are several good reasons to expect that embryo screening for late-onset diseases and non-disease traits (such as gender and eye colour) will not become widespread, at least in the near future:
- Embryo screening is only possible for couples undergoing IVF. Given the substantial financial costs of IVF, its currently low success rate, and general unpleasantness, it’s unlikely that it will become the default mode of reproduction for fertile couples in the near future – particularly when the alternative strategy is free, simple, and vastly more enjoyable.
- Embryo screening is simply not feasible for most common diseases and complex traits. I’ve covered this before: basically, we now know that the majority of common diseases (e.g. type 2 diabetes and obesity) and complex trait (e.g. height and athletic performance) are affected by hundreds to thousands of different genetic variants, each with very small effect. That means that there is no “perfect” human being; all of us (and all of our potential embryos) have slightly increased risk of some diseases, and slightly decreased risk of others. So instead of being able to select a “disease-free” embryo, parents will face a difficult and unpalatable choice between embryos with a range of slightly different disease susceptibilities.
- Genetic screening for complex adult-onset diseases will become redundant as medicine improves. Why invest money in genetic screening for conditions like type 2 diabetes or coronary heart disease when it’s highly likely that almost all of these conditions will be completely treatable by the time your child reaches the age of susceptibility? Similarly, the value of selecting for intelligence-boosting alleles will likely be massively outweighed by other approaches to improving academic performance. This was one of the most unrealistic aspects of the movie Gattaca – what, a society with the technology to screen embryos can’t devise a treatment for a minor heart defect?
Note that the objections above only hold true for common, late-onset diseases and other complex traits; it’s clear from the survey that screening for severe early-onset disease (like muscular dystrophy or severe mental retardation) is already attractive to parents, and I’d expect this to soon become near-universal among couples using IVF.
If you’re already investing tens of thousands of dollars in the IVF procedure, and screening is available, it would require a very strong moral objection to refuse. After all, it’s not like you’re actually discarding any more embryos than you normally would be; you’re simply using additional information to decide which of the embryos to implant.
The same actually holds true for selecting on the basis of “cosmetic” traits: if a couple if already undergoing IVF, I can’t think of any convincing moral objection to them using whatever arbitrary criteria they like to decide which of their dozen or so embryos to implant. Indeed, I expect parental demand will drive the inclusion of complex disease genes and “cosmetic” traits in the standard genetic screen for IVF embryos, although this will make for some very difficult decisions. Most of the moral objections to this process seem to rest on the vague notion that it somehow “devalues” human life; call me idealistic, but I suspect that parents will love their IVF-conceived children just as much regardless of whether they were randomly plucked from a Petri dish or selected on the basis of genetic information.
This freedom won’t result in a generation of blue-eyed, blond-haired children, for two reasons. Firstly, this outcome would require a universality of preferences for certain traits that simply doesn’t exist. Such a dramatic outcome is no more likely than a generation of girls all called “Susannah”. Similarly, while its clear that the availability of pre-natal gender testing can result in a skew in male/female frequencies (see China, India), this will likely ultimately correct itself as a low frequency of one sex increases its attractiveness to parents. And secondly, it’s important to emphasise that this screening will only occur in parents undergoing IVF, who are likely to remain a substantial minority for the foreseeable future.
There’s little doubt that there will be a gradual shift towards widespread testing for seriously nasty variants even in couples conceiving naturally, either through carrier screening (a la Counsyl) or non-invasive testing of embryos using foetal DNA present in the mother’s blood (like the tests for Down syndrome and other diseases developed by Sequenom). However, neither of these technologies makes widespread screening for complex traits or common diseases feasible, unless you seriously believe that couples would terminate a pregnancy on the basis of a 0.7% increase in rheumatoid arthritis risk.
In summary: we are moving into a world in which genetic screening for severe, early-onset diseases will likely become commonplace, and where testing for non-disease traits among IVF participants will also occur. However, don’t believe the hype: it’s highly unlikely that the world of “designer babies” routinely selected on the basis of height and IQ, as predicted by social conservatives and scare-mongering media, will ever become a pervasive reality.
Feighanne Hathaway, Esther Burns, Harry Ostrer (2009). Consumers’ Desire towards Current and Prospective Reproductive Genetic Testing Journal of Genetic Counseling DOI: 10.1007/s10897-008-9199-3