The notion of parents picking out genetically perfect babies may seem like science fiction, but bioethicists warn in a new report that some companies have already started to offer couples going through in vitro fertilization (IVF) the means to pick better embryos through polygenic scoring.
Polygenic scores are a "weighted average of the contributions of all of the genes we have information on in the genome, to try to predict whether one person has a higher or lower rate of a disease or some trait," explained Patrick Turley, an assistant professor of research with the University of Southern California's Center for Economic and Social Research, in Los Angeles.
Couples might be tempted to use polygenic scoring to pick embryos predicted to have specific traits they treasure, hoping to produce kids who are taller, smarter, or less likely to develop cancer or heart disease. However, polygenic scores aren't as predictive right now as genetics companies might claim, and there are a lot of potential pitfalls about using them to select an embryo, the experts argue.
"People are just lousy at understanding probabilities. We're just not good at it and that's what polygenic scores involve," said Michelle Meyer, assistant director of research ethics with Geisinger Health System's Center for Translational Bioethics and Health Policy in Danville, Penn. "They aren't guarantees at all. They are very much predictions, and they are infinitely worse than predictions about the weather, which we all know are imperfect."
But even though the technology is currently flawed, it is expected to improve as scientists expand their understanding of genetic risk.
As it does, this service will open up the possibility of a future where there will be genetic haves and have-nots, Meyer added.
Given the disparities already present in medicine, it's not too far-fetched to consider, said Meyer, who co-authored a report on the trend in the July 1 issue of the New England Journal of Medicine.
"You're going to have a narrow segment of society who is more likely to benefit from [polygenic scoring] than others, so there's some danger of furthering disparities," Meyer said.
For the moment, experts are mainly concerned that prospective parents are being given false promises related to polygenic scoring of embryos.
Still an uncertain science
Genetics firms have promised polygenic scoring of embryos that will weigh risk of cancer, heart disease, high blood pressure, high cholesterol, inflammatory bowel disease, Alzheimer's disease, intellectual disability, dwarfism, and a host of other common medical conditions, the researchers noted in their report.
Scientists just don't know enough about human genetics to make firm promises that these scores will have significant bearing on the individual traits of such "chosen" children, Meyer said.
"There's a lot of risk and uncertainty, and we worry about whether people really know that," Meyer said. "Companies don't have the incentive to help consumers understand the limitations of the service that they're offering. Their built-in incentive is to emphasize and perhaps overemphasize the benefits and underemphasize the limitations."
For example, parents might want to use polygenic scoring to reduce the risk of having a child of short stature.
But a child chosen in this manner could be expected to be just 1 inch taller than average, "an outcome that is unlikely to be practically meaningful and that in any case might surprise parents who believe they had successfully selected against short stature," the report stated.
There's also a serious danger of unintended consequences, given that individual genes often perform multiple duties in humans, Turley noted.
"Genes don't usually do just one thing. When you select an embryo based on a decreased risk...
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