Getting pregnant: New study finds female eggs actually choose their sperm
The genetic equivalent of ghosting?
According to a brand new study, if the egg likes a sperm, it's chemicals tell it to swim faster ... However, if it doesn't, it sends out signals to encourage it to put on the breaks.
It was researchers at Stockholm University and the Manchester University NHS Foundation Trust who discovered that actually, what we have believed about how conception happens might be wrong – instead of the strongest sperm being the one that makes it to the egg and voila – becomes the one who 'makes it' it turns out we might have to flip things on its head. Because according to the new study, it looks like, actually, it is all about the egg choosing which sperm it likes better and giving that one a little nudge to come on and get the job done.
“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,” explains John Fitzpatrick, an Associate Professor at Stockholm University.
Once the sperm have made it all the way up the fallopian tube to meet the egg, it's no longer just about who swam the fastest because at the end of the fallopian tube sperm comes into contact with these aforementioned chemoattractants in the follicular fluid.
And this is when the egg gets all picky and basically decides who it wants to make a baby with, and who can just pack it in and go home.
Fitzpatrick explains, “When sperm goes into the follicular fluid, they start to go straighter and they start to change the way they swim. 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.”
In other words – if the egg likes a sperm, its chemicals tell it to swim faster, fight harder and basically the job done. If it doesn't, it sends out chemical signals to encourage it to put on the breaks.
Professor Daniel Brison, the Scientific Director of the Department of Reproductive Medicine at Saint Marys' Hospital and a senior author on this study was delighted by the findings. “The idea that eggs are choosing sperm is really novel in human fertility,” he says. “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.”