Having too few “friendly” vaginal bacteria may increase a woman’s chance of ovarian cancer, and swabs can be used to spot this, say researchers.
The team, led by University College London, hope the finding could be used to identify women at high risk of the cancer, which has no screening test.
However, they say that more work is needed to explore this.
It is too soon to recommend women should be given protective doses of the good bacteria, they say.
About ovarian cancer
More than 7,300 women are diagnosed with ovarian cancer each year in the UK.
Many women are not diagnosed until the cancer has already started to spread.
If your doctor thinks your symptoms could be due to ovarian cancer they will recommend blood tests and scans.
Now researchers believe micro-organisms living inside our bodies may also play a role.
There is growing scientific evidence that the community of bacteria and other microbes that reside inside us – our microbiome – influence our wellbeing and health.
One species of beneficial bacteria that is thought to be particularly important in the vagina is called lactobacillus.
Experts believe it stops other unhelpful or bad microbes from taking up residence and causing harm.
The study involved 176 women with ovarian cancer, 109 with inherited high-risk genes for ovarian cancer (BRCA1 genes) and 295 women with no known genetic risk.
The women were examined and samples taken using the same collection method used in cervical screening.
Lactobacilli levels were significantly lower in the women under 50 with ovarian cancer or high-risk cancer genes.
What do the findings mean?
It is not clear whether this link is causal or if other factors might explain it, or how much of an impact it has on risk.
The investigators believe good bugs provide a protective barrier to other infections, stopping them from travelling up the gynaecological tract to the fallopian tubes and ovaries.
Researcher Prof Martin Widschwendter said: “We do not yet know for sure whether low levels of the beneficial bacteria leads to an increased risk of ovarian cancer, but that is what we suspect.
“It fits with other research. It’s been shown that women who use excessive vaginal hygiene products have lower levels of this bacterium too, and they are at increased risk of ovarian cancer.”