New study reveals it's not actually the 'best sperm' that fertilises the egg

A new fertility study has challenged what many of us believe about human reproduction: that it’s the ‘best sperm’ that fertilises the egg.

In fact, it might be the egg that ‘chooses’ the sperm it likes best, according to researchers from Stockholm University and the Manchester University NHS Foundation Trust.

According to this research, the egg releases chemicals telling it to swim faster if it likes the sperm.

And if it doesn’t, it uses chemicals to encourage it to slow down.

John Fitzpatrick, Associate Professor at Stockholm University said, “Human eggs release chemicals called chemoattractants that attract sperm to unfertilised eggs. We wanted to know if eggs use these chemical signals to pick which sperm they attract.”

He added, “When sperm go into the follicular fluid, they start to go straighter and they start to change the way they swim.

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“So depending on the strength of that signal, you can get different responses in how the sperm are responding to these female chemical signals within their follicular field.”

These findings go against what many of us believe about reproduction, where the ‘best sperm’ swims the fastest and fertilises the egg.

Professor Daniel Brison, the Scientific Director of the Department of Reproductive Medicine at Saint Marys' Hospital was a senior author on the study.

He revealed he was delighted by the findings, saying, “The idea that eggs are choosing sperm is really novel in human fertility.”

In addition, further research into this could even help with fertility treatments in humans.

John added, “Research on the way eggs and sperm interact will advance fertility treatments and may eventually help us understand some of the currently ‘unexplained’ causes of infertility in couples.”

So not only do women choose their partners, it might be their egg that chooses the 'best' sperm too!