Scientists have used a tiny plastic “obstacle course” to test how much sperm would struggle to navigate during sex in the weightlessness of space.
Some particularly resilient sperm still made it through the course, suggesting that conceiving children in space will still be possible, according to research published on March 26 (2026).
However, a bigger problem could be that the development of embryos after fertilisation was harmed by a lack of gravity, the Australian team of researchers found.
With humanity setting its eyes on colonising space – Nasa launched its first crewed mission around the Moon in half a century on April 1 (2026) – scientists have been studying how difficult it will be to procreate on spaceships or other worlds.
One of the biggest challenges is that sperm will no longer be pulled downwards by Earth’s gravity.
“Sperm need to actively find their way to an egg, and this study is the first to put that ability to the test under space-like conditions,” said study senior author and The University of Adelaide Sperm and Embryo Biology Group head Dr Nicole McPherson.
The scientists used a plastic chamber that resembles the female reproductive tract to act as a “miniature obstacle course”, the senior lecturer said.
“Think of it as a tiny race track ... sperm are introduced at one end and have to swim their way through to the other.”
Both human and mice sperm were sent down the course, which was inside a device that uses constant rotation to simulate the microgravity of space.
The sperm was about 50% worse at navigating through the course, compared to how they perform under Earth’s gravity.
This worked out to be roughly a 30% drop in successful fertilisation, according to the study in the journal Communications Biology.
However, the sperm that did make it through seemed to produce better-quality embryos, which could turn out to be “beneficial”, Dr McPherson said.
It appeared that the stress of microgravity acted as a “filter” that effectively cleared the field, “leaving only the most capable sperm in the running”, she explained.
A bigger problem came in the first 24 hours after the sperm had fertilised the eggs.
“The results reversed sharply, with fewer embryos formed, and those that did were of poorer quality,” she said.
This suggests that microgravity “may not be the deal-breaker we feared, but protecting the embryo from weightlessness in those critical first hours will likely be essential for reproduction in space”, she added.
Some people, including billionaire SpaceX founder Elon Musk, have ambitious plans to make humans an interplanetary species by establishing settlements on the Moon, followed by Mars.
There has also been speculation that the first baby conceived outside the bounds of Earth could be the result of a couple having sex on a flight launched by the booming space tourism industry.
ALSO READ: Want to travel to space, gentlemen? You might return with erectile dysfunction
Dr McPherson emphasised that much more research is needed to understand how reproduction works in space, adding that fertilisation is “only one small piece of a very long and complex puzzle”.
“We are still a long way from seeing the first space baby,” she said. – By Daniel Lawler/AFP
