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If you’ve ever tried to get pregnant, you’ll almost certainly have heard that it helps if a woman lies still after her partner ejaculates. But this is unlikely to make a difference, a study suggests.

The idea is that lying down for a while gives the sperm time to reach their destination egg. The same theory has been applied to intra-uterine insemination (IUI), a fertility treatment that involves injecting sperm directly into a woman’s uterus.

“There’s a lot of anxiety that after IUI if you stand up, everything will fall out,” says of the University of Southampton, UK.

Some research has backed up the theory. Some in 2009 and found that 15 minutes of bed rest improved IUI success rates, leading to more pregnancies. But now at the VU University Medical Center Amsterdam in the Netherlands and her colleagues have conducted a larger study.

The team randomly assigned 479 women receiving IUI to either 15 minutes of bed rest or to get up and move around straight after treatment. Most of the women had several rounds of treatment – in total, the group collected data on almost 2000 IUI cycles.

They found that 32 per cent of the cycles that incorporated bed rest resulted in pregnancy, but 40 per cent of cycles that involved immediate movement were successful. “In our opinion, immobilisation after IUI has no positive effect on pregnancy rates,” says van Rijswijk. “There is no reason why patients should stay immobilised after treatment.”

Although the results contradict previous findings, they make sense. For example, it is known that sperm can survive in the uterus for several days – there is no reason why bed rest would affect this, says van Rijswijk, who presented the findings this week at the in Helsinki, Finland.

Our crude understanding of female anatomy is partly to blame for the theory, says , chair of the . Anatomical illustrations often depict the uterus and vagina as directly aligned, with a straight-line passage from uterus to vagina to the outside world. In reality, our internal organs are somewhat tilted, he says.

Van Rijswijk doesn’t know if rest improves the chances of conceiving naturally because no studies have fully investigated this, she says. But the findings undermine the “lying still, feet-in-the-air” advice given to many women trying to conceive, says Macklon.

https://youtu.be/6XuEgYXJAwE

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