Professor Alastair Sutcliffe of the Institute of Child Health at UCL said the research provided mixed news. "Compared to other women in the UK of the same age range and time frame, we found the rates of breast and uterine cancer were no different to UK women as a whole." But there was an increased risk of ovarian cancer, he said.
The authors of the report conclude: "Certain results argue against an association with assisted reproductive technology itself, but others leave open the possibility it might affect risk."
The risk is still small: just 15 in every 10,000 patients developed ovarian cancer in the study period. The figure is around 11 in 10,000 generally.
Professor Geeta Nargund, medical director of Create Fertility which has five clinics in the UK, said the findings were concerning. "We should be moving towards milder stimulation and fewer drugs."
Dr Adam Balen, professor of reproductive medicine at the University of Leeds, said: "This study, from a huge database, suggests that women who have IVF with certain conditions, such as endometriosis, may be at increased risk of developing ovarian cancer."
But charities said IVF patients should not be overly alarmed.
Dr Julie Sharp, head of health information at Cancer Research UK, said: "This is important research, but doesn't prove fertility treatment increases ovarian cancer risk."
The research was presented at the annual conference of the American Society for Reproductive Medicine in Baltimore.