A faulty gene has been identified that increases the risk of ovarian cancer more than threefold.
About 18 women in every 1000 develop the disease. But this risk increases to about 58 in every 1000 who have the mutated BRIP1 gene, scientists say.
The defective gene prevents cells carrying out proper repairs to their DNA, eventually leading to cancer.
Researchers also found women with the mutation were more likely to be diagnosed with aggressive, later-stage ovarian cancers at an older age.
Professor Paul Pharoah, of the Cancer Research UK Cambridge Institute, said: "Our work has found a valuable piece of the puzzle behind ovarian cancer and we hope that our work could eventually form the basis of a genetic test to identify women at greatest risk.
"Finding these women will help us prevent more cancers and save lives. This would be important in a disease like ovarian cancer, which tends to be diagnosed at a late stage when the chances of survival are worse."
Each year about 7100 UK women are diagnosed with ovarian cancer and more than 4200 women die from the disease.
Nell Barrie, Cancer Research UK's senior science information manager, said: "Research like this, which looks at inherited genetic changes and how they can affect a woman's risk, is vital. We urgently need ways to detect ovarian cancer early, as the cancer is often diagnosed when it's too late for effective treatment because the cancer has already spread."
The findings are reported in the Journal of the National Cancer Institute.
