A recent study found the risk of a rare brain tumour doubled among women using hormonal contraception, including the pill, for five years or more.

But the controversial study is being rapidly dismissed by other researchers and experts.

The large-scale study used data from Denmark’s entire female population of reproductive age (15–49) between 2000 and 2009.

From this huge pool, researchers found 317 glioma diagnoses.

Now, emeritus director of the MIMR-PHI Institute of Medical Research at Monash University, Professor Henry Burger, says the increased risk is very minor indeed.

“In my view, the findings are of no biological or clinical significance,” he told industry press Medical Observer.

“[The findings are] negligible in comparison with the benefits of the medications.

“The authors present only relative risks, not absolute risks, for a tumour they say affects about five women per 100,000 per year in the quoted age range.

“Any increase in risk of less than one per 1000 per year is regarded as rare – the worst-case result here is an absolute increase in risk of five per 100,000 per year or one in 20,000 women using a hormonal contraceptive,” he said.

Other experts say the benefits of hormonal still outstrip the risks outlined in the paper.

“For example, a 20-year-old woman who takes the oral contraceptive for 10 years will reduce her chance of getting ovarian cancer by about 15 in 1000,” said Paul Pharoah, professor of cancer epidemiology at the University of Cambridge, UK.

“A much bigger reduction than any possible increase in the risk of brain cancer.”

“Suppose... all these women changed to a less effective form of contraception and 10,000 of them got pregnant: we would then expect one extra mother and 40 extra babies to die,” said Professor Sir David Spiegelhalter, Winton Professor of the Public Understanding of Risk, University of Cambridge.