In order to "harvest" as many eggs as possible for a cycle of IVF, women are given drugs to stimulate their maturation in the ovary.

However, there have been long-term concerns that ovarian stimulation may increase the risk of breast, uterine and ovarian cancers, particularly if the woman undergoes several cycles of IVF in her lifetime.

But a study by the London School of Hygiene and Tropical Medicine, published in the journal Human Reproduction, found no link.

The researchers looked at the incidence of cancer in 5,556 women who attended the Hallam Medical Centre, a large infertility clinic in London, between 1975 and 1989.

Our findings will be reassuring for anyone who has undergone ovarian stimulation treatment for infertility, or is considering doing so

Dr Pat Doyle, London School of Hygiene and Tropical Medicine

In each case the women had at least one cycle of infertility treatment.

They were divided into two groups, those who had received drugs to stimulate ovulation, and those who had not.

The researchers found the incidence of breast, uterine and ovarian cancers in the women was no greater than expected for the general population.

They found no evidence for a link between ovarian stimulation and increased cancer incidence.

Reassurance

Researcher Dr Pat Doyle said: "Our findings will be reassuring for anyone who has undergone ovarian stimulation treatment for infertility, or is considering doing so, and for specialists offering infertility treatments to couples experiencing difficulties conceiving."

However, Dr Doyle said that the women in the study were relatively young - by the end of the follow up period their average age was still only 46.

She said: "It is possible that these treatments could have adverse effects later in life.

"We will be following up on the women as they grow older, to give us a better picture of any long-term implications for ovarian stimulation treatments."

Relief

Dr Simon Fishel, director of the Care In The Park Clinic in Nottingham, was among the first researchers to question whether fertility drugs were linked to an increased risk of ovarian cancer.

He told BBC News Online: "This is hugely welcome, and a great relief to practitioners as well as patients.

"However, I would say that the numbers of cases of ovarian cancer normally peak in the fifth and sixth decade, and so it is important to follow women into their 50s and 60s to ensure that there is no higher incidence of cancer.

"For that reason I would say we are not completely out of the woods yet, even though this is extremely encouraging."

Dr Fishel said that getting pregnant was in itself a way to reduce the risk of ovarian cancer.