MORE than one in five women has been unfaithful to a long-term partner and 90 per cent confess to having thought about it, a study shows.
Paula Yates / File
Cheating heart ... Paula Yates.
Researchers found that almost all women in a relationship have considered being unfaithful, but whether they actually cheat on a partner or not depends on their genes.
Experts say that certain women possess a set of "infidelity genes" which make them twice as likely to be unfaithful as others.
Lead researcher Professor Tim Spector, of St Thomas Hospital in London, said: "Thinking about infidelity is nearly universal. Ninety per cent of women admitted to having had thoughts about infidelity at some time.
"But whether or not they are unfaithful may to some extent depend on their genes."
Professor Spector's findings come from a study of female twins, which showed that our tendency to cheat is largely genetic and likely to run in families.
He hopes to conduct further studies with male twins and added: "I do believe we would have similar findings in men."
The study could help explain why the late TV presenter Paula Yates's infidelity mirrored that of her parents. She began an affair with rock star Michael Hutchence in 1995 while married to Bob Geldof.
Later she discovered she was not, as previously thought, the daughter of Stars on Sunday host Jess Yates but of his rival Hughie Green, with whom her mother had had an affair soon after marrying Yates.
Professor Spector looked at 1600 pairs of female twins. Some were identical, sharing all their genes, and some non-identical, meaning they share around 50 per cent of their genes.
The women filled in questionnaires about their love lives, including whether they had ever been unfaithful to a long-term partner or husband.
Overall, 22 per cent admitted having cheated at some point in their lives.
Professor Spector said the figure doubled to around 44 per cent among women with an identical twin sister who had been unfaithful. It increased to 33 per cent among women with a non-identical twin sister who confessed to infidelity.