International guidance on 14-day limit to growing human embryos ‘relaxed’ by scientists

The limit has not been lifted by the International Society for Stem Cell Research but where scientific rationale is justified, researchers will be allowed to grow a human embryo for more than 14 days

The limit on early human embryo research was set 40 years ago (Getty)

Guidance that prevents scientists from growing and studying human embryos in a dish beyond 14 days is to be “relaxed” under landmark changes unveiled by an international consortium of experts.

The International Society for Stem Cell Research (ISSCR), which oversees and shapes the universally followed guidance, has not gone as far as to lift the limit but says it would be open to reviewing and scrutinising proposed research that seeks to examine the culturing of human embryos beyond the current two weeks.

It raises the prospect of further exploration of the genetic and biological mechanisms that drive the early formation of human life and could allow scientists to understand the development of birth defects and congenital abnormalities better.

The guidance was set 40 years ago and in some countries, including the UK, it is actually illegal to grow and to study a human embryo for more than 14 days.

However, following advances over the past four decades, the ISSCR has acknowledged that this limit can be exceeded in instances in which the scientific rationale is provided and justified.

Professor Robin Lovell-Badge, chair of the ISSCR’s guidelines group, said: “It’s very conditional, so we’re definitely not giving the green light yet,” adding that the rules have been “relaxed” but “we haven’t abandoned them”.

Professor Kathy Niakan, a member of the group, said that any experiment involving the culture of human embryos beyond 14 days cannot start until it has been approved by the ISSCR, respective regulators in each country and other health authorities.

“We call for the national academies of sciences, academic societies, funders [and] regulators to lead public conversations touching on the scientific significance as well as the social and ethical issues that are raised by allowing such research,” she said.

Prof Niakan highlighted that the research of this kind would depend on the laws and regulations of each country. The UK would need to change its legislation on human embryo experiments while both the US and China have not set laws.

She added: “We want there to be no doubt: this is not a green light for groups to go ahead with extending human cultures beyond 14 days. It would be irresponsible and in many jurisdictions it would be illegal to do so.

“Instead, the guidelines are a call to proactively engage in a two-way dialogue with the public to review the 14-day limit.”

There are a number of “real rationales” for wanting to study a human embryo for more than two weeks, Prof Lovell-Badge said.

He pointed to congenital abnormalities that develop “quite early” in the embryo during its divisional phase. These defects can kill thousands of babies each year. Congenital heart disease affects about eight in every 1,000 babies.

He said: “We have very few things that are used to prevent these [defects] ... but by understanding these early stages better, you’ll be able to adopt simple procedures to reduce the amount of suffering.”

Scientists have said the ability to uncover why an embryo might have abnormalities through experiments on intact embryos maintained beyond 14 days, and by using new technologies to avoid or correct the problem, the frequency of selective abortion or prenatal deaths might be reduced.

Professor Janet Rossant, another member, said the group had “very in-depth discussions” on the 14-day rule and considered introducing a new 28-day limit.

However, it eventually decided against this as, “the problem with that is that it depends on the scientific question, the issue you’re trying to deal with”.

Instead, “every single experiment that is proposed is going to have to be justified in terms of the particular timeline it’d be studied under”.

Prof Lovell-Badge said the original 14-day rule had been introduced as a “compromise” between scientific groups who wanted to allow early human embryo research and those “who didn’t want any at all”.

As such, the introduction of a new 28-day limit would be similarly improper, he said. “Simply choosing a different timescale would again be arbitrary,” Prof Lovell-Badge added. “It’s far more important that the reason for doing experiments is really looked at properly and justified properly.”