The first time Jamie Cassidy was pregnant, the fetus had a genetic mutation so devastating that she and her husband, Brennan, decided to terminate in the second trimester. The next time they tried for a baby, they weren’t taking chances: They would use IVF and screen their embryos’ DNA. They wanted to avoid transferring any embryos with the single-gene mutation that had doomed their first pregnancy. And then they started wondering what other ailments they could save their future son or daughter from.
The Cassidys’ doctor told them about a company, Genomic Prediction, that could assess their potential children’s odds of developing conditions that aren’t tied to a single gene, such as heart disease, diabetes, and schizophrenia. The test wouldn’t be any more invasive than screening for a single gene—all the company needed was an embryo biopsy. The science is still in its early stages, but the Cassidys didn’t mind. Brennan has Type 1 diabetes and didn’t want to pass that condition on, either. “If I can forecast that my baby is going to have less chance to have Type 1 diabetes than I did, I want that,” he told me. “I’d burn all my money to know that.”
Thanks to more sophisticated genetic-testing techniques, IVF—an expensive, invasive treatment originally developed to help people with fertility troubles—is becoming a tool for optimizing health. A handful of companies offer screening for diseases and disorders that range from life-threatening (cancer) to life-altering (celiac disease). In many cases, these conditions’ genetic links are poorly understood or weak, just one factor of many that determine whether a person develops a particular condition. But bringing another human being into the universe can be a terrifying-enough prospect that some parents are turning to extensive genetic testing to help pick their future offspring.
Genetic screening has been a crucial part of IVF—and pregnancy—for decades. Medical guidelines recommend that any aspiring mother should be given the option to test her own DNA and find out whether she risks passing on dangerous genes, a practice known as carrier screening. If both parents carry a particular mutation, doctors will likely suggest IVF and embryo screening. These measures are traditionally limited to conditions linked to single-gene mutations, such as Huntington’s disease, most of which are exceedingly rare and seriously affect a child’s quality of life. During IVF, embryos are also typically screened for chromosomal abnormalities to help avoid miscarriages, and generally nonheritable conditions such as Down syndrome.
As the scientific understanding of the genome has progressed, companies including Genomic Prediction and a competitor called Orchid have begun offering a test that promises a more comprehensive investigation of the risks lurking in an embryo’s genes, using what’s known as a polygenic risk score. Most common ailments aren’t connected to a single gene; polygenic risk scores aim to predict the lifetime likelihood of conditions, such as diabetes, in which many genes contribute to a person’s risk. Consumer DNA-testing companies such as 23andMe use these scores to tell customers whether they have, say, a slightly above-average likelihood of developing celiac disease, along with a disclaimer that lifestyle and other factors can also influence their chances. These risk scores could theoretically help identify customers who, say, need a colonoscopy earlier in life, or who need to double down on that New Year’s resolution to eat healthier. But the current scientific consensus is that polygenic risk scores can’t yet provide useful insights into a person’s health, if indeed they ever will.
Analyzing an embryo’s DNA to predict its chances of developing genetically complex conditions such as diabetes is an even thornier issue. The tests, which can run thousands of dollars and are typically not covered by insurance, involve sending a small sample of the embryos to the companies’ labs. In the United States, such tests don’t need to be approved by the FDA. Genomic Prediction even offers customers an assessment of which embryos are “healthiest” overall. But the control these services offer is an illusion, like promising to predict the weather a year in advance, Robert Klitzman, a Columbia University bioethicist and the author of the book Designing Babies, told me. A spokesperson for the American Society for Reproductive Medicine told me there aren’t enough quality data to even take a position on whether such tests are useful. And last year, the American College of Medical Genetics and Genomics published a lengthy position statement concluding that the benefits of screening embryos for polygenic risk were “unproven” and that the tests “should not be offered as a clinical service.” The statement raised the possibility that people might undergo extra, unnecessary rounds of IVF in search of ever healthier embryos.
Genomic Prediction published a rebuttal to the ACMG that cited, among other research, several studies led by company researchers that concluded that among siblings, those with a lower risk score were significantly less likely to have a given condition. The truth is, though, the effect of screening embryos for polygenic risk won’t be clear until the embryos chosen to develop into fetuses are born, grow up, and either develop diabetes or don’t. Genomic Prediction and Orchid both told me that humanity shouldn’t have to wait that long for the insights their tests provide. Polygenic risk scores are “one of the most valuable pieces of information that you can get,” Orchid’s founder and CEO, Noor Siddiqui, told me. Nathan Treff, Genomic Prediction’s chief science officer, was similarly bullish. “Everybody has some kind of family history of diabetes, cancer, and heart disease. So we really don’t have a situation where there’s no reason for testing,” he told me.
Many of the experts I spoke with about these tests are concerned that people might opt into IVF because they’re chasing certainty that companies can’t really promise. A study last year found both high interest and approval among Americans when it comes to screening embryos for polygenic risk. For now, most of the customers I interviewed used advanced tests that included polygenic risk because they were going through IVF anyway. Many of Genomic Prediction’s customers using the scores are participants in a clinical trial. But Tara Harandi-Zadeh, an investor in Orchid, told me she planned to do IVF even though she and her husband have no fertility issues or history of genetic disease. Harandi-Zadeh is especially worried about de novo mutations—genetic changes that occur spontaneously, without any hereditary link. She wants to screen her embryos to weed out monogenic diseases and plan for the risks of polygenic ones. “If I have that information, I can help my child at the stages of life to be able to get treatment or tests or just prepare for it,” she said. Treff told me that people like Harandi-Zadeh make up a small percentage of Genomic Prediction’s customers, but their numbers are growing.
Scientists just don’t understand enough about the genome to confidently predict what any single embryo will be like should it go on to become a person. Most genes influence many facets of our being—our health, our physical traits, our personality—and only a fraction of those interactions have been investigated. “You don’t know the full package,” Klitzman said. “Bipolar disorder is associated with creativity. So if you screen out bipolar disorder, you may also be screening out genes for creativity, for instance.” Because no embryo is completely risk-free, future parents might also have to decide whether they think, say, a risk of diabetes or a risk of heart disease sounds worse. A paper out last week put it this way: “The expected reductions in disease risk are modest, at best—even if the clinical, ethical and social concerns are dismissed.”
Those concerns are significant. More and more people are already turning to IVF for reasons other than infertility. Some select their children based on sex. Jeffrey Steinberg, a fertility doctor with clinics in the U.S. and internationally, offers eye color selection and told me he is working on height. Orchid assesses genetic risk for some autism-spectrum disorders, and Genomic Prediction plans to add a similar screening to its catalog. A paper published last week argued that editing embryos—not just testing them—could mitigate genetic risk for a variety of conditions, while also acknowledging it could “deepen health inequalities.” (In the U.S., clinical trials of embryo editing cannot be approved by the FDA, and public funds cannot be used for research in which embryos are edited.) Critics say that even if technology could cut the prevalence of diseases like diabetes, doing so could drive discrimination against those born with such “undesirable” traits. Social services and support for people with those conditions could also erode—similar concerns have been raised, for example, in Iceland, where pregnancy screenings have all but eliminated Down-syndrome births.
Even if the science does catch up to the ambitions of companies like Genomic Prediction, genetics will never guarantee a child a healthy life. “Of the 100 things that could go wrong with your baby, 90 percent of them or more are not genetic,” Hank Greely, the director of the Center for Law and the Biosciences at Stanford University, told me. That’s partly why the Cassidys decided to ignore most of their screening results and simply select the embryo that didn’t have the monogenic mutation that Jamie carried, and had the lowest risk of diabetes. “We’re not trying to have a kid that’s 6 foot 2 and blond hair and blue eyes and going to go to Harvard. We just want a healthy baby,” Brennan told me.
Their son was born in 2023 and so far has been at the top of the curve for every developmental marker: He’s big and tall; he talked and walked early. It will be years, probably, before they know whether or not he’s diabetic. But it’s hard, they said, not to feel that they picked the right embryo.
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