The 14-day limit for human embryo research should be extended to 28 days, the fertility regulator has recommended in a move that could pave the way for breakthroughs in understanding the causes of miscarriages and heart defects.
If adopted in law, this would permit scientists to cultivate embryos to the equivalent of 28 days of development for the first time, allowing them to study a crucial “black box” period. They say this could help uncover the origins, and develop new screening tools, for recurrent miscarriages and severe conditions such as spina bifida.
“The Human Fertilisation and Embryology Authority [HFEA] has recommended that the law is changed to extend the time limit on embryo research,” Peter Thompson, the HFEA’s chief executive, told the Guardian after announcing the proposals at the Progress Educational Trust’s annual conference in London on Wednesday.
Speaking at the conference, Thompson outlined how significant scientific advances since the Human Fertilisation and Embryology Act was introduced in 1990 mean that it is now increasingly possible for researchers to develop and sustain embryos beyond 14 days. In recent years, he said, scientific advances “have begun to push against the boundaries of the act”.
In 2021, the influential International Society for Stem Cell Research removed post-day-14 research from its list of “prohibited” scientific activities and scientists have been calling for the UK to follow suit. Now, the HFEA has also concluded that the limit should be extended as part of sweeping changes that it says are needed to modernise the UK’s fertility law.
“Research after 14 days would lead to different insights – an understanding of early embryo development in the ‘black box’ period, which could, for example, identify early pregnancy problems or improve our understanding of how congenital diseases start to develop,” Thompson told the conference. “The hope of course is that such discoveries would in turn lead to new treatment options.”
The changes would be consistent with the embryo’s “special status”, Thompson said, adding that the UK public appears largely supportive, although some remain opposed to any form of embryo research.
The HFEA is also considering how fertility laws should be revised to accommodate the advent of lab-grown eggs and sperm, which Thompson said could be “a genuinely disruptive technology” in future. New rules are also required to regulate so-called stem cell-based embryo models, embryo-like structures grown without the use of eggs or sperm. Scientists are unclear whether these entities have the biological potential of developing into a foetus.
For embryo research, the HFEA recommends an upper limit of 28 days, with researchers required to make case-by-case applications to culture embryos between 15 and 28 days of development. Any decisions surrounding the modernisation of fertility law is ultimately a matter for parliament, Thompson said, as the new limit would require a change in law.
When introduced in 1990, the 14-day limit was theoretical as scientists could not cultivate embryos beyond a few days. But as this capability has advanced – primate embryos have been cultivated to about day 25 – studying human embryos has remained off-limits between day 14 and day 28, when researchers are able to rely on embryos donated to research after miscarriages or terminations.
This has left crucial steps in development, such as implantation into the womb, neural tube formation and the heart tube starting to pump blood, almost entirely inaccessible to scientific research.
Dr Peter Rugg-Gunn, of the Babraham Institute in Cambridge, welcomed the proposed changes, which he said would help uncover the initial causes of serious pregnancy conditions such as pre-eclampsia, foetal growth restriction and stillbirth.
“These conditions occur in 10% of all pregnancies,” said Rugg-Gunn. “Although these conditions are first detected much later in pregnancy, it is thought that they might arise early on in development – between days 14 and 42 – due to errors in placental formation. There is currently no means to study this.”
A relaxation in the rules could also help advance the ability to screen for other severe conditions in development, such as neural tube misfolding, heart defects, skeletal abnormalities and certain types of cancer, which are thought to emerge between about day 21 and day 35.
Sarah Norcross, the director of Progress Educational Trust, a charity to advance public understanding of science, law and ethics, said: “The regulator has recognised that there are strong scientific and ethical arguments for culturing human embryos beyond the time currently permitted under UK law. Such an extension will not only help scientists to understand human biology and disease, but also maximise the usefulness of a very precious resource – embryos donated to research by fertility patients, following the completion of their treatment.”
