It's time to relax the rules on growing human embryos in the lab Create an account

A week more would help

Chris Leschinsky/Getty

By Sam Wong

WHEN it comes to studying our earliest existence, how far are we willing to go? Growing human embryos in the lab beyond the seventh day after fertilisation – the moment when embryos normally implant in the wall of the uterus – has been a long-standing challenge for biologists, but the latest research is allowing us to extend past that.

Earlier this year, a team led by Ali Brivanlou at Rockefeller University, New York, and another group at the University of Cambridge managed to keep embryos alive for longer than seven days, but they stopped the experiments two weeks in.

It’s not that the embryos perished. Guidelines set by national medical societies in the US prohibit growing embryos in the lab for more than 14 days. In the UK and 11 other countries, that limit is enshrined in legislation, and embryos must be destroyed before they develop further.

Until now, this restriction wasn’t an issue, but as science has caught up with the law, many researchers are eager to revisit the rule. Clearly, experimenting on well-developed embryos (or fetuses, past the 12th week from conception) would be ethically unacceptable to almost everyone, but that doesn’t mean we shouldn’t go beyond the first two weeks. The question is, how far, and to what end?

Magdalena Zernicka-Goetz, who led the Cambridge group, wants to open the “black box” surrounding this period of our lives. “It’s one of the most critical phases of our early development and we don’t know anything about it,” she says. By extending the limit we could learn why many pregnancies are lost in the early stages, for example, and ...