People who undergo IVF treatment have an increased risk of developing breast cancer, a study suggests.
Data from more than 626,000 women over 21 years found links indicating that women over 40 who have IVF are 65% more likely to develop the disease.
The increased risk across all ages was 10%.
In preparation for IVF, women are given drugs to stimulate the ovaries into producing more eggs.
This increases levels of oestrogen in the body, which scientists at Copenhagen University believe may explain the cancer link.
Professor Geeta Nargund, from St George’s Hospital, London, told the Telegraph that women are more prone to breast cancer as they get older, particularly if they have never given birth to a child.
“On top of that if you add stimulation drugs which increase oestrogen levels, this risk further appears to be increased,” she explained. “This is a wake-up call about the use of high dose stimulation in IVF, especially in women over the age of 40.”
Overall, the risk of developing cancer in the age range of the women in the study was low, equivalent to a 0.6% chance of getting breast cancer with no IVF, compared to a 0.8% chance with IVF following the treatment.
The study was presented at the European Society of Human Reproduction and Embryology conference in Vienna.