Women who use fertility drugs may be at increased risk of developing cancer of the uterus. Dr Ronit Calderon-Margalit and colleagues at Hadassah-Hebrew University in Jerusalem studied 15,000 women who gave birth 30 years ago. They found that those who used fertility drugs were more likely to develop uterine cancer - cancer of the womb - than women who had not used fertility drugs, but the risk was still low.

Of 567 women who took fertility drugs, 5 had developed uterine cancer in the past 30 years, three times the incidence of women who had not used fertility drugs. For women who had used the drug Clomiphene, the risk was four times greater.

The study, published in the American Journal of Epidemiology, also found smaller increases in the risk for other cancers: melanoma, breast cancer and non-Hodgkin's lymphoma. The researchers did not find an increased risk of ovarian cancer with fertility drug use, a link which has been identified in previous studies.

Jodie Moffat, health information officer at Cancer Research UK, said the study had several limitations, and it was difficult to draw any firm conclusions about the link between fertility drugs and uterine cancer. 'The study didn't include a detailed history of fertility drug use, and the number of women who developed uterine cancer was very small', she said.

Richard Kennedy, consultant at the Centre for Reproductive Medicine at University Hospital Coventry, and spokesman for British Fertility Society, also said that 'there have been a high number of studies that have failed to find a conclusive link. It is important to remain vigilant about these things but the broad message must be reassurance'.

Fertility drugs are used by women who are undergoing IVF treatement, egg donation, or to facilitate conception. They act by inducing ovulation, stimulating more egg production or, like Clomiphene, by blocking the hormone estrogen.