Experts at New York University studied 256 pregnant women and found that those who developed gestational diabetes had significantly higher levels of periodontal bacteria and inflammation than women who remained healthy.
The experts believe that the inflammation associated with gum disease may interfere with the normal functioning of insulin, contributing to the onset of gestational diabetes.
"In addition to its potential role in preterm delivery, evidence that gum disease may also contribute to gestational diabetes suggests that women should see a dentist if they plan to get pregnant, and after becoming pregnant," said Dr Ananda Dasanayake, a professor of epidemiology and health promotion in the university's College of Dentistry.
He added: "Treating gum disease during pregnancy has been shown to be safe and effective in improving women's oral health and minimising potential risks."
The findings are published in the Journal of Dental Research.