Starting a family beyond Earth could be more challenging than expected. New research from Adelaide University shows that sperm struggle to navigate in low gravity, suggesting that gravity plays a key role in helping them reach an egg.
Scientists from the Robinson Research Institute, the School of Biomedicine, and the Freemasons Centre for Male Health and Wellbeing studied how space-like conditions affect sperm navigation, fertilization, and early embryo development.
To simulate microgravity, researchers used a 3D clinostat machine developed by Dr. Giles Kirby at Firefly Biotech. This device continuously rotates cells to mimic the disorienting effects of zero gravity. Sperm from three different mammals, including humans, were tested by sending them through a maze designed to resemble the female reproductive tract.
“This is the first time we have been able to show that gravity is an important factor in sperm’s ability to navigate through a channel like the reproductive tract,” said senior author Dr. Nicole McPherson from Adelaide University’s Robinson Research Institute.
“We observed a significant reduction in the number of sperm that were able to successfully find their way through the chamber maze in microgravity conditions compared to normal gravity.
“This was experienced right across all models, despite no changes to the way sperm physically move. This indicates that their loss of direction was not due to a change in motility but other elements.”
Progesterone May Help Guide Sperm
The researchers also found that adding the sex hormone progesterone improved how well human sperm navigated under simulated microgravity conditions.
“We believe this is because progesterone is also released from the egg and can help guide sperm to the site of fertilization, but this warrants further exploration as a potential solution,” said Dr. McPherson.
Fertilisation and Embryo Development Affected
The team examined how exposure to microgravity during fertilisation influences early embryo development in animal models.
After four hours in simulated zero gravity, the number of successfully fertilized mouse eggs dropped by 30 per cent compared to normal Earth conditions.
“We observed reduced fertilization rates during four-to-six hours of exposure to microgravity. Prolonged exposure appeared to be even more detrimental, resulting in development delays and, in some cases, reduced cells that go on to form the fetus in the earliest stages of embryo formation,” said Dr. McPherson.
“These insights show how complex reproductive success in space is and the critical need for more research across all early stages of development.”
Why Gravity Matters for Reproduction
Earlier research has explored how sperm move in space, but none had tested their ability to navigate through a reproductive channel under controlled conditions like this.
The findings were published in Communications Biology.
This study was conducted in collaboration with Adelaide University’s Andy Thomas Centre for Space Resources, which focuses on the challenges of long-term space exploration and living beyond Earth.
“As we progress toward becoming a spacefaring or multi-planetary species, understanding how microgravity affects the earliest stages of reproduction is critical,” said Associate Professor John Culton, Director of the Andy Thomas Centre for Space Resources.
Future Research on Reproduction in Space
The next phase of the research will explore how different gravity environments, including those on the Moon, Mars, and in artificial gravity systems, affect sperm navigation and early embryo development.
A key question is whether these effects change gradually as gravity decreases or if there is a threshold where changes occur suddenly, creating an “all or nothing” response.
Answering this will be essential for planning human reproduction in future Moon and Mars settlements and for designing artificial gravity systems that support healthy development.
“In our most recent study, many healthy embryos were still able to form even when fertilized under these conditions. This gives us hope that reproducing in space may one day be possible,” said Dr. McPherson.