THURSDAY, May 27, 2021 (HealthDay News) — An international standard that limits how long human embryos can be grown in a laboratory has been extended under limited conditions, which will remove a barrier to stem cell research.

But the International Society for Stem Cell Research did not specify how much longer embryos could be grown beyond the 14-day limit specified in 2016 guidelines, the Associated Press reported. That restriction has blocked research of a crucial period in embryo development, typically between 14 and 28 days, according to Robin Lovell-Badge, a stem cell expert at the Crick Institute in London and chair of the group that wrote the new guidelines.

“We think a lot of congenital abnormalities are developing quite early during this period,” said Lovell-Badge, the AP reported. “By understanding these early stages better, it might allow us to adopt simple procedures to reduce the amount of suffering.”

But not everyone is comfortable with the new guidelines, and some worry they could allow human embryos to be grown at more advanced stages in the lab. Marcy Darnovsky, executive director of the Center for Genetics and Society, told the AP that it is tough to find scientific justification for the new guidelines. “When an embryo is in a petri dish outside the body, are you going to really be able to tell anything meaningful about miscarriage or embryonic development?” she said. Darnovsky was also worried the guidelines do not impose a limit on how long human embryos could potentially be grown.

The new guidelines do prohibit human cloning, transferring human embryos into an animal uterus, and the creation of human-animal chimeras, saying such work “lacks scientific rationale or is ethically concerning.”

Associated Press Article

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