The marker is an antibody to a protein, called mesothelin, which is overproduced by cancer cells.
The study found the antibody was present in high levels in the blood of many women who were infertile because of problems with their ovaries.
Researchers think elevated antibody levels may indicate that the body's immune system is attacking its own ovaries, a condition called autoimmune oophoresis.
Autoimmune oophoresis is known to cause infertility, and researchers think it may also lead to some cases of ovarian cancer, though it's not clear how.
"That's the 64 million dollar question," says study researcher Judith L. Luborsky, PhD, professor of pharmacology, obstetrics and gynecology and preventive medicine at Rush University Medical Center in Chicago.
"The question we don't have an answer to is what role the immune system actually plays in the initiation [of cancer]," she tells WebMD.
While the idea is interesting, experts who were not involved in the research say the study only looked at one moment in time, so it's tough to draw conclusions about what elevated antibody levels may mean and it doesn't prove that elevated antibodies cause cancer.
"It sort of creates another hypothesis," says Mary Daly, MD, PhD, professor and chair of the department of clinical genetics at Fox Chase Cancer Center, in Philadelphia.
"There's a lot of literature linking infertility with an increased risk for ovarian cancer, but very little to suggest why that would be," Daly says. "What is it about women who have problems getting pregnant that puts their ovaries at increased risk for ovarian cancer?"
This study may help to direct research into one of the possible explanations for that, she says.