IT'S not easy being beautiful.
And if you are easy on the eyes, it's apparently even harder to remain faithful.
A new study has revealed that beautiful women may be more likely to have affairs because of a sex hormone linked to attractiveness and flirtatiousness.
Oestrogen, the so-called female hormone, affects fertility and has been shown to make women dress more provocatively and show more thrill-seeking behaviour.
Dr Kristina Durante of The University of Texas at Austin and colleagues found that young women felt more attractive when they had high levels of an oestrogen known as estradiol, and they acted on those feelings.
'Women with higher estradiol reported a greater likelihood of flirting, kissing and having a serious affair with someone other than their primary partner and were marginally more likely to date another man,' DrDurante's team wrote in the Royal Society Journal Biology Letters.
'Results provide support for the relationship between physical beauty and fertility and suggest that women high in reproductive health engage in opportunistic serial monogamy - being open to affairs and moving on to a new relationship if a higher-quality mate becomes available.'
The high-oestrogen women also reported more sexual behaviour - especially outside of a relationship, although it was not linked to one-night stands.
'Our results are consistent with the possibility that highly fertile women are not easily satisfied by their long-term partners and are especially motivated to become acquainted with other, presumably more desirable, men,' the study concluded.