Study Finds Eggs Are Very Choosy When It Comes to Sperm

Turns out the egg makes the final call

The egg only releases chemicals attracting a very selective group of sperm.
Getty Images/Science Photo Libra

Selecting the father of one’s children is generally a very personal choice, but it turns out it may actually be one your eggs make for you.

A new study has found that eggs are very selective when choosing sperm for fertilization. In the study, published Tuesday in the journal Proceedings of the Royal Society, researchers looking at leftover samples from 16 couples getting reproductive treatment found that eggs release a chemical that attracts only certain kinds of sperm, and they don’t seem too inclined to take their owner’s personal choice of mate into account.

“We expected to see some sort of partner effect, but in half of the cases the eggs were attracting more sperm from a random male,” study author John Fitzpatrick, an assistant professor in the department of zoology at Stockholm University in Sweden, told CNN. “The most likely explanation for this is that these chemical signals allow females to choose males who are more genetically compatible.”

During ovulation, eggs release chemicals known as chemoattractants, which help sperm find the egg. In the study, however, researchers found that only 18 percent of sperm can actually pick up on the signal, which Fitzpatrick suggests may help weed out less desirable sperm by only attracting the most genetically compatible matches.

Senior author Daniel Brison, the scientific director of the department of reproductive medicine at Saint Mary’s Hospital in the UK, said the discovery could have positive implications for the future of infertility treatment.

“The idea that eggs are choosing sperm is really novel in human fertility,” he said. “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.”

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