Women using IVF are a third more likely to develop ovarian cancer, the biggest study of fertility treatment in the world has discovered.
Scientists at University College London said underlying problems in infertile women may be driving the increased risk, but warned the finding leaves open the possibility the procedure itself might be to blame.
Previous studies suggested ovarian stimulation used to harvest eggs could fuel cancer but most specialists dispute the danger. However, British experts said the new findings were serious enough to consider regular screening of IVF patients.
They called for infertile women to be informed the risk of ovarian cancer was higher than in natural conception.
Researchers studied every IVF procedure recorded by the Human Fertilisation and Embryology Authority in Britain from 1991 to 2010 - more than 250,000 women.