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Human embryo research: how to move towards a 28-day limit

The decades-old limit on how long human embryos can be grown in culture is under debate. A new road map outlines how to extend the length of culture responsibly.
By
  1. Alejandro De Los Angeles

    1. Alejandro De Los Angeles carried out this work while a research fellow in medicine at Harvard Medical School, Boston, Massachusetts, USA.

  2. Nissim Benvenisty

    1. Nissim Benvenisty is a professor of genetics at the Hebrew University of Jerusalem, Israel.

  3. Hongkui Deng

    1. Hongkui Deng is a professor at Peking University in Beijing, China.

  4. Jacob H. Hanna

    1. Jacob H. Hanna is a professor of stem-cell pluripotency and synthetic embryology at the Weizmann Institute of Science, Rehovot, Israel.

  5. Julian Koplin

    1. Julian Koplin is a lecturer in bioethics at Monash University, Clayton, Australia.

  6. Tianqing Li

    1. Tianqing Li is a professor at the Kunming University of Science and Technology, Kunming, China.

  7. Pentao Liu

    1. Pentao Liu is a professor at the University of Hong Kong, Hong Kong, China.

  8. Yuin-Han Loh

    1. Yuin-Han Loh is a professor at the A*STAR Institute of Molecular and Cell Biology in Singapore.

  9. Duanqing Pei

    1. Duanqing Pei is a professor at Westlake University in Hangzhou, China.

  10. Ryohichi Sugimura

    1. Ryohichi Sugimura is an assistant professor at the University of Hong Kong, Hong Kong, China.

  11. Timothy Theodore Ka Ki Tam

    1. Timothy Theodore Ka Ki Tam is an honorary research associate at the University of Hong Kong, Hong Kong, China.

  12. Tan Tao

    1. Tan Tao is a professor at the Kunming University of Science and Technology, Kunming, China.

  13. Alan Trounson

    1. Alan Trounson is emeritus professor at Monash University, Clayton, Australia.

  14. Shao Xu

    1. Shao Xu is a PhD student at the University of Hong Kong, Hong Kong, China.

  15. Leqian Yu

    1. Leqian Yu is a professor at the Institute of Zoology and Chinese Academy of Sciences, Beijing, China.

  16. Elias Zambidis

    1. Elias Zambidis is a professor in oncology and paediatrics at the Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.

  17. Magdalena Zernicka-Goetz

    1. Magdalena Zernicka-Goetz is a professor of biology and biological engineering at the California Institute of Technology, Pasadena, California, USA.

  18. Robin Lovell-Badge

    1. Robin Lovell-Badge is a senior group leader at the Francis Crick Institute in London, UK.

An embryologist prepares an embryo for in vitro fertilization using a microscope.

The 14-day rule for embryo research is a regulatory limit currently used in several countries. Credit: Smita Sharma/New York Times/Redux/eyevine

In December, the UK national fertility regulator — the Human Fertilisation and Embryology Authority (HFEA) — recommended that the government extend the length of time for which human embryos can be grown in culture from 14 days to 28.

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Nature 643, 31-34 (2025)

doi: https://doi.org/10.1038/d41586-025-02016-9

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Competing Interests

The Zernicka-Goetz laboratory developed stem-cell-derived embryo models and the method to culture human embryos until day 14. J.H.H. was granted (through the Yeda–Weizmann Institute of Science) patents relevant to embryo models and ex utero embryogenesis, and is a co-founder and chief scientific adviser of Renewal Bio, which has licensed technologies mentioned above.

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