For the first time, scientists have managed to edit a dangerous gene mutation from human embryos using a technique known as Crispr or Cas9. This was the first time such a trial was conducted in the United States, where the scientists erased an inherited heart defect from the embryos, a paper in the journal Nature said. The genetic defect can lead to heart failure and death.

The trial was conducted by an Oregon Health and Science University researcher, Shoukhrat Mitalipov. The embryos were only allowed to develop for a few days and the scientists had no intention to implant them, The Washington Post reported. The clinical trials can now move forward. Scientists think that a single gene mutation in all the body’s cells could account for more than 10,000 diseases, the World Health Organisation says.

Though the US does not allow the use of federal funds for embryo research, scientists think the gene-editing study was justified as it did not design an embryo, but edited mistakes. The National Academies of Sciences, Engineering and Medicine had allowed the research to continue, and had sent recommendations that were followed, the researchers said.

News of the edited embryos sparked a much larger debate about gene research and the ethics of such practices. Marcy Darnovsky, executive director of the Center for Genetics and Society, said research like this can lead to doctors offering “genetic upgrades” to babies.

“Once those commercial dynamics kick in, we could all too easily find ourselves in a world where some people’s children are considered biologically superior to the rest of us,” The Washington Post quoted her as saying. “We need to ask ourselves whether we want to add that new kind of excuse for extreme social disparities to the ones we already tolerate.” However,reproductive endocrinologist Paula Amato at the Oregon university said such technology could rescue” embryos with gene defects.