The Modern Laboratory · People

A chemist at heart. Henry Leese studied physiological chemistry at the University of Reading, graduating with first class honours in 1966. He took his PhD at Imperial College London in 1969 and moved that year to the University of York as a research fellow. After a year at ETH Zurich on a Royal Society fellowship, he returned to York, where he spent his whole career. He rose from lecturer to reader and was Professor of Biology from 1997 to 2010. He is now Emeritus Professor of Biology at Hull York Medical School.

Listening to one embryo. To learn what an embryo needs, you must measure what it takes in and gives out. Leese wanted to do this for a single living embryo, without harming it. With his PhD student David Gardner he measured the nutrients taken up by single mouse embryos from tiny drops of fluid around them. Their paper appeared in 1986 in the first issue of Human Reproduction. Because the embryo survives the measurement, the same idea can be used on an embryo that may still go on to be transferred.

Learning from nature. He also studied the oviduct, the tube where an embryo spends its first days. In 1990 he and Gardner reported the levels of nutrients in mouse oviduct fluid and how they affected embryos in culture. Later work in his laboratory looked at how the lining of the oviduct makes its fluid. The aim was always the same: to let the dish resemble the body a little more.

The quiet embryo. In 2002 he set out the “quiet embryo” hypothesis in BioEssays. It proposed that the embryos most likely to thrive often have a calmer metabolism, using just what they need. He and colleagues returned to the idea in later papers, including one in 2016 that compared it to the Goldilocks principle: not too much, not too little.

Honours. He spent 1980 to 1981 as a visiting associate professor at Harvard Medical School. He was made an honorary member of the Association of Clinical Embryologists in 2002 and a Fellow of the Royal College of Obstetricians and Gynaecologists in 2003. The Society for Reproduction and Fertility awarded him its Marshall Medal in 2010. He was President of the British Fertility Society from 2015 to 2018 and gave its Patrick Steptoe Lecture in 2016. In 2026, forty years after their first paper, teacher and student wrote together again in Human Reproduction, on how the measurement of single embryos came about.

The IVF Museum · The Modern Laboratory · People
Compiled with AI-assisted research and checked against the original sources. Not yet peer-reviewed. Corrections are warmly welcomed.