The study, led by researchers from the university’s Robinson Research Institute, School of Biomedicine at the University of Adelaide and Freemasons Centre for Male Health and Wellbeing, examined how space-like conditions affect sperm movement, fertilisation and early embryo development.
To simulate zero gravity, scientists used a specialised 3D clinostat developed by Dr Giles Kirby at Firefly Biotech. The device rotates cells to disorient them, mimicking the conditions experienced in space. Sperm from three mammal species, including humans, were then tested in a maze designed to replicate the female reproductive tract.
Lead author Dr Nicole McPherson said the findings revealed gravity plays a crucial role in sperm navigation.
“This is the first time we’ve been able to show gravity is an important factor in helping sperm find their way through a channel like the reproductive tract,” she said.
The team found a marked drop in the number of sperm successfully reaching their target under simulated microgravity, despite no change in how they physically moved. This suggests the issue is not with motility, but with orientation and guidance.
Researchers also discovered that adding progesterone, a hormone essential for establishing pregnancy, helped human sperm partially overcome the disorientation caused by microgravity. The hormone is naturally released by the egg and may act as a chemical signal to guide sperm, although further research is needed.
The study also explored how microgravity affects fertilisation and early development. In animal models, exposure to zero gravity conditions resulted in a roughly 30 per cent decline in successful fertilisation rates after four hours. Longer exposure led to developmental delays and, in some cases, fewer cells forming in the earliest stages of embryo growth.
The findings, published in Nature Portfolio journal Communications Biology, highlight the complexity of reproduction in space.
The project was conducted in collaboration with the Andy Thomas Centre for Space Resources, which focuses on the challenges of long-term space exploration and living off Earth.
Centre director Associate Professor John Culton said the research is vital as humanity edges closer to becoming a spacefaring species.
“As we move towards living beyond Earth, understanding how microgravity affects the earliest stages of reproduction is critical,” he said.
Researchers are now moving into the next phase, investigating how different gravity environments such as those on the moon and Mars, as well as artificial gravity systems influence sperm navigation and embryo development.
A key question is whether these effects occur gradually as gravity decreases, or if there is a tipping point where reproductive success sharply declines.
Despite the challenges, Dr McPherson said the results offer cautious optimism.
“Encouragingly, we still observed healthy embryos forming under these conditions,” she said. “It suggests reproduction in space may one day be achievable.”