Research has found that taking aspirin before sex may increase a woman's likelihood of conceiving a boy, if the woman has had a history of miscarriages.
The theory goes that in some cases, the immune system can see an embryo as a foreign intruder, promoting an inflammatory response in the body.
As male embryos are thought to be more vulnerable to these changes in the body than female embryos, the inflammation can reduce the chances of having a boy.
In a recent study at the Eunice Kennedy Shriver National Institute of Child Health and Human Development, in the US, scientists put the theory to the test.
As part of the research, 1228 women with a history of miscarriages were given a low dose aspirin to take before sex, for as long as they were trying to get pregnant.
Out of the all the women who took part, some were given a placebo pill.
Data showed 31 per cent of the women who had taken aspirin had conceived a boy, compared to 23 per cent who had been on the placebo.
Research also found that women who were taking aspirin and had given birth to a boy had an overall lower rate of inflammation in the body, compared to the other participants in the study.
The findings led researchers to conclude that aspirin before conception can reduce the chance of a male embryo being rejected.
Fertility expert Professor Simon Fishel told the Daily Mail that while the studies were interesting, more research would be needed, especially into why taking aspirin has an affect on some women, but not others.
"Importantly, it relates only to women who have had miscarriages and evidence of inflammation," he said. "It does not have any bearing on sex ratios in normal conceptions, where aspirin will not increase the chances of having a boy."
Aspirin is a non-steroidal anti-inflammatory, commonly used to treat pain, fever and inflammation. Several small trials have shown that it can also increase the pregnancy rate among women undergoing IVF.