Sex in space could be lethal, a study has announced - and not just because doing anything that vigorous in a pressurised tin can 220 miles above Earth is generally a bit risky.
According to a study by biologist Dr Anja Geitmann of Montreal University, there is evidence to show that cells in low gravity have difficulty communicating with each other, and grow at below normal rates.
The fear is that if an astronaut were to become pregnant while in space it could lead to severe health problems for both the mother and baby.
In fact a developing foetus could be at risk of brain disease, cancer and illnesses like Alzheimer's, the study suggests.
In the study, which is published in PLOS One, Geitmann looked at how pollen tubes work in space. When a pollen grain is normally transferred to the stigma it grows into a pollen tube to help more male reproductive cells reach the 'egg'.
In this - and the 'cylindrical tool' involved - Geitmann saw similarities to the way humans reproduce, and by simulating both zero gravity and high gravity in a spinning centrifuge she was able to test how they were affected in different conditions. (This was helped by the fact that pollen tubes grow incredibly quickly - useful when you're renting massive equipment from the European Space Agency.)
She found that the pollen tubes grew smaller in lower gravity, and were wider in hypergravity. Meanwhile intracellular traffic flow, the way that cells communicate, was badly affected.
Since hinderances in this traffic flow can cause many health problems in humans, particularly during pregnancy, Geitmann concluded that sex in space was actually an incredibly risky endeavour.
"Our findings have implications for human health as similar effects are likely to occur in human cells such as neurons where long distance intracellular transport is crucial," Geitmann told the Daily Mail.
Occasionally rumours pop up that astronauts might already have crossed this particular frontier, and Gizmodo points out that Nasa doesn't specifically forbid it.
For its part, the space agency has always denied that sex has taken place in space, however, and it has a strict behaviour code which demands "professional standards" aboard its craft. But if humans are going to form colonies in space or other planets one day, we'll have to come up with a solution - and not just so that some pair of future astronauts can claim bragging rights.