If you'd prefer not to fall pregnant, best you avoid the rhythm method of contraception because no matter how closely you watch your fertility cycle to ensure you avoid having sex during ovulation, nature still has one-up on you.
It turns out that semen, long believed to serve simply as a vehicle for a man's little swimmers, actually contains a substance that helps to trigger pregnancy-inducing hormonal reactions in woman... including ovulation, say experts.
Scientists have known for a while that an ovulation-inducing factor (OIF) exists in some species' semen, such as camels and rabbits, however scientists in China have been researching the possibility of OIF in semen from mammals since as far back as 1985. Their hunch was not shared by the rest of the scientific world. In fact, it was mostly ignored, says reproductive biologist, Gregg Adams.
Adams and his team only began testing this hypothesis two decades later and were surprised to find a significant ovulatory response to seminal fluid in their test animals which included llamas - an animal closely related to the camel.
This finding sparked continued research for OIF and Adams says they have managed to identify one protein and surprisingly found it to be one that is present in several species, including humans. They found the protein acted as a hormone in the female body, telling it to get its baby-making equipment ready.
Adams is now asking whether or not the levels of OIF substance in semen affect a man's fertility - a question which could assist couples battling to fall pregnant.