Why women enjoy s e x more on certain days

Monthly mood swings may help women to get pregnant, according to a new study.

A team of US scientists have discovered that fluctuations in levels of the female sex hormone oestrogen affect the responsiveness of the brain's "reward system", with a peak in the first part of the menstrual cycle.

This reward system dictates the amount of pleasure attained from various activities, whether it be from having sex or from eating chocolate.

"Increased activity of the brain's reward system at this time could boost anticipation and enjoyment of sexual activity," said Dr Karen Berman of the US National Institute of Mental Health, who worked on the study published in the Proceedings of the National Academy of Sciences.

"This demonstrates for the first time that female hormones affect the reward system in very specific ways during particular parts of the cycle," added Dr Berman, who went on to stress that the results did not mean that women are more emotional or vulnerable to hormones than men.