Then they looked for new mutations, variants in the baby's genome that it doesn't share with either parent. These "de novo" variants can be totally benign, but this is also how some rare genetic disorders arise, like Down syndrome or Turner's syndrome and some others. Using computational techniques, the team found 39 of the baby's 44 de novo mutations, while it was still a fetus. But they also wrongly predicted 25 million other potential de novo mutations, as Science Now points out. These numbers could suggest a fetus has a genetic disorder it doesn't actually have, and could needlessly worry the parents. Still, it shows the technique works, Shendure says. Eventually, this non-invasive prenatal sequencing could become routine practice.