[In Depth] Human embryo research confronts ethical ‘rule’
Researchers studying human embryos in the lab have always hit a roadblock at about 7 days—the point where the embryo would usually attach to the uterus. Now, two teams report growing human embryos about a week past that point, revealing key differences between the development of human and mice embryos. The limit now isn't technological, but ethical: a widely held rule that dictates all embryo research should be stopped at 14 days. Now that culturing methods have finally made it possible to reach this point, some scientists and bioethicists are saying the rule should be revisited. But that won't be welcomed by those who consider the rule to have a firm moral grounding—nor by those who oppose all research on human embryos. Author: Patrick Monahan