"First baby born after full genetic screening of embryos," says the headline. The announcement, issued last week by the Oxford Biomedical Research Centre and the European Society of Human Reproduction and Embryology, celebrates the birth of a healthy boy, thanks to a technique called "next-generation sequencing," which scans embryos for chromosomal and genetic abnormalities. In the Philadelphia Inquirer, the beaming mom and dad pose with their adorable son, Connor.
Connor is just the latest in a long line of firsts. Every year or so, doctors herald the arrival of a new embryo test, certified by the birth of a healthy baby. But the babies you hear about are the lucky ones. For every success, there are dozens, hundreds, or thousands of embryos that failed the evaluation. You won't see their pictures, because they're never born. They're flushed away.
In 2002, the Journal of the American Medical Association announced the successful application of preimplantation genetic diagnosis to Alzheimer's disease. The authors hailed it as "the first known PGD procedure . . . resulting in a clinical pregnancy and birth of a child free of inherited predisposition to early-onset AD." The baby was one of 15 embryos subjected to the test. Seven, cursed with the unwanted mutation, had been discarded.
A year later, the story was frozen embryos. "First birth after preimplantation genetic diagnosis performed on thawed embryos," said the article. Again, the failures were marginalized. Ten embryos had been thawed. Eight had been screened. Five had been transferred to the uterus. One had survived.
As testing became cheaper and easier, its application spread. "First embryo screening birth," the BBC announced. "A British woman has given birth to a child which was screened as an embryo to make sure it was healthy — even though there was no family history of genetic disorders." Below the headline, Baby Tom wriggled endearingly. "We are so happy," his mother exulted. "It is a dream come true."
In 2005, another breakthrough arrived: "First Birth Using Pre-Implantation Genetic Diagnosis To Save Baby From Rhesus Blood Disease." Then came a whole new technology: pre-implantation genetic haplotyping. "The first UK babies have been born after a pioneering embryo test," said the report. At the top of the page was a photo of the happy couple and their children. At the bottom was a diagram with a small note in the corner: "If problem found, embryo destroyed."
In 2009, we got more good news. "The first baby tested preconceptionally for a genetic form of breast cancer (BRCA1) has been born," said the press release. "The mother and her little girl are doing very well." That description wasn't quite true: The test had been done after conception. The baby was one of 11 embryos checked for the bad gene. Six had been discarded for flunking the test. Three more had been rejected for "other abnormalities."
Then another new technology emerged: array comparative genomic hybridization. "Woman gives birth to world's first baby from IVF egg-screening technique," said the headline. The more controversial applications, to embryos and fetuses, were set aside.
Now comes "next generation sequencing," heralded by Baby Connor. His parents began with 13 embryos. Three passed the test. One made it all the way.
Embryo screening hasn't made the world a sadder place. It has made it better. It has prevented cystic fibrosis and other terrible diseases. If you worry about unborn life, it's better to catch genetic problems early, at the preimplantation stage, than to discover them in the womb many weeks later and abort the pregnancy. Many chromosomal tests, such as the one used on Connor, help doctors discern which embryos are most likely to survive pregnancy. In this way, they enable the development of life. And the application of these tests to eggs, rather than embryos, bypasses the moral question of killing.
But we shouldn't be too sanguine. Our success in testing embryos for fatal childhood diseases has emboldened us to test them for genes that might never hurt them, such as BRCA1. We're discarding embryos over the possibility of breast cancer, which rarely strikes before age 30, and early-onset Alzheimer's, which doesn't begin till 40 or 50. We're rejecting them to avoid the risk of conditions such as rhesus blood disease, where onset is dubious (specific antibodies have to cross the placenta to the fetus) and the cure rate is 70 to 95 percent. We're even chucking embryos just because their genes make them useless as tissue donors. That, too, was hailed as a triumph when the first sibling donor was born 13 years ago. "Healthy baby brother shows power of genetic medicine to bring hope," said the Associated Press headline.
We didn't invent the cruelty of genetic misfortune or the ruthlessness of selection. Nature did. For every creature that thrives today, trillions died. They failed as embryos, individuals, or species. They're the invisible denominator, the universe of darkness in which the light of vibrant life momentarily flickers. Now the light has brought forth a species that transforms selection itself. We govern the choosing and the extermination. We celebrate our victories. We hide the tragedies and the cost.
Sleep well, Baby Connor. You're the happy ending of the only story we choose to tell.
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Saletan (@saletan) covers science, technology and politics for Slate.
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