Women diagnosed with cervical and uterine cancer have been warned that the disease can be aggravated by semen.
The study, conducted by scientists from Britain and South Africa on behalf of the Medical Research Council, found that semen contains large levels of hormones that increase the size of blood vessels, causing the growth of the tumour.
The high prostaglandin levels in semen are believed to be responsible and researchers are urging women to avoid making the condition worse.
"Sexually active women who are at risk of cervical or uterine cancer should encourage their partners to wear a condom to prevent increased exposure to the prostaglandins that might make their condition worse," commented head of the research, Dr Henry Jabbour.
He added that the research highlights the potential for a new therapeutic approach that will tackle both possible sources of prostaglandin - those produced naturally by women and those introduced to the body by sperm.
The disease is believed to kill one in three sufferers in the UK.