WOMEN who have kids using IVF are more likely to develop breast cancer, a study suggests.
The drugs used to stimulate their ovaries may increase tumour risk by up to 65 per cent.
Experts described the findings as a “wake-up call” and said patients should be told of the peril.
Researchers analysed data on 625,712 Danish women, who were tracked for up to 21 years.
Some received assisted reproductive treatment, such as IVF, and others did not.
Those in the assisted group were 10 per cent more likely to get breast cancer than the other.
But the risk rose far higher in women who had their first child through IVF aged 40 or older.
They were 65 per cent more likely to get the disease than those conceiving naturally at the same age.
IVF usually involves giving women strong drugs that stimulate the ovaries to grow more eggs.
But this increases levels of the hormone oestrogen, which fuels some breast cancers.
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The University of Copenhagen medics said the altered hormones could be to blame.
Prof Geeta Nargund, of St George’s Hospital, London, added: “This is a finding of great significance.
“This is a wake-up call about the use of high dose stimulation in IVF, especially in women over the age of 40.
“It highlights the need to counsel women about their potential health risk in the future.
“The use of drugs and dosages should be minimised.” Dr Jane Stewart, chair of the British Fertility Society, said: “We shouldn’t be complacent about long term effects.
“Previous studies have been reassuring regarding breast cancer but clearly the discussion is not closed.” Eight in every 1,000 treated women got breast cancer, compared with six in 1,000 in the other group.
Dr Roy Farquharson, of Liverpool Women’s Hospital, said the finding should not cause alarm.
He added: “The findings should spark further studies to confirm an increased risk.” Ditte Vassard, who worked on the study, said: “An increased risk could be due to age-related vulnerability to hormone exposure or to higher doses of hormones during ART treatment.”
Breast cancer is the most common form of the disease in the UK, with 55,000 cases yearly.
Older women, and those who are childless or infertile, are known to have a higher risk.
The findings were presented at the annual meeting of the European Society of Human Reproduction and Embryology in Vienna, Austria.
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