Space babies could be off the cards! Human sperm may get LOST in zero gravity, study claims

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Having babies in space might be more difficult than first thought – as researchers have discovered sperm can get lost in zero gravity.

The idea of reproduction beyond the bounds of Earth has become a hot topic, with some saying it must become a 'top priority' to preserve the future of mankind.

However, a new study has identified a major hurdle that people will face while trying to conceive in space.

Sperm are negatively impacted by a lack of gravity, which plays havoc with their directional skills, according to researchers from Adelaide University.

'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,' senior author Dr Nicole McPherson said.

'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.'

Researchers have found the navigational abilities of sperm are negatively impacted by a lack of gravity

Sperm in microgravity 'got lost' significantly more often than usual – and it could have important implications for future human reproduction on other planets 

For their study the researchers took sperm samples from humans, mice and pigs and put them through a machine that simulates zero gravity.

The sperm then travelled through a maze designed to mimic the female reproductive tract – and 'got lost' significantly more often than usual.

Using simulation models, they observed up to a 30 per cent reduction in the number of eggs that were successfully fertilised by the sperm.

Overall, fertilisation rates were reduced during four–to–six hours of exposure to microgravity.

Prolonged exposure appeared to be even more detrimental, resulting in development delays.

In some cases, it reduced the number of crucial cells that go on to form the foetus in the earliest stages of embryo formation.

'These insights show how complex reproductive success in space is and the critical need for more research across all early stages of development,' Dr McPherson said.

In good news, however, the team found that the addition of the sex hormone progesterone helped more human sperm overcome the negative effects of microgravity on navigation.

Exposure to zero gravity also appeared to modify the number of foetal cells within the embryo. The left image shows the cells in normal gravity, compared to in microgravity (right)

'We believe this is because progesterone is also released from the egg and can help guide sperm to the site of fertilisation, but this warrants further exploration as a potential solution,' Dr McPherson said.

The study, published in the journal Communications Biology, is the first to assess sperm's ability to navigate through a reproductive channel under these controlled conditions.

'As we progress toward becoming a spacefaring or multi–planetary species, understanding how microgravity affects the earliest stages of reproduction is critical,' co–author Professor John Culton said.

The researchers now want to investigate how varying gravitational environments and proposed artificial gravity systems impact sperm navigation and early embryo development.

A key question is whether gravity–related changes in development occur gradually as gravitational force decreases.

Or, it could be that there is a very low threshold, resulting in an 'all or nothing' response.

Understanding this distinction is essential for planning future human reproduction in extraterrestrial environments, including 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 fertilised under these conditions,' Dr McPherson said. 'This gives us hope that reproducing in space may one day be possible.'

Reproduction in space is not as easy as in Hollywood movies such as 1979 Bond film Moonraker make out 

The study reads: 'Space exploration continues to inspire scientific advancement, with a renewed focus on long–term missions and planetary settlements.

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'NASA's ARTEMIS program aims to return humans to the Moon by 2029, while SpaceX anticipates its first crewed Mars missions by 2030.

'As humanity moves toward permanent off–Earth habitation, understanding how extraterrestrial conditions affect reproduction is essential for crew health and the sustainability of life beyond Earth.'

Last year, researchers from Kyoto University showed that mouse egg and sperm cells could survive in space and go on to produce healthy offspring.

Meanwhile, Dutch Biotech startup Spaceborn United have launched the first miniature lab for in vitro fertilisation (IVF) and embryo processes into orbit.