Research led by Professor Steven Offenbacher, from the University of North Carolina, has found that mothers who have gum disease in early pregnancy may be more at risk of going into labour prematurely.
Professor Offenbacher's work is the second major study this year to suggest such a link.
His work is based on a study of 357 pregnant women, who were tested for gum disease when they were less than 26 weeks pregnant and again three days after the birth of their baby.
The results indicate that those women who had gum disease at the beginning of the trial had a higher rate of going into labour at less than 37 weeks, and in a small number of cases, at less than 34 weeks.
A baby is said to be premature when it is born more than three weeks early. Full term is 40 weeks.
Lower birth weight
The results also indicate that these women have a higher rate of low birth weight babies and that worsening gum disease during pregnancy significantly increases the risk of developing pre-eclampsia - a condition that can be fatal for both mother and child.
Professor Offenbacher said: "The results of the trial indicate that the effect of gum disease in pregnancy seems to be as harmful as other well established risk factors such as smoking.
"The next step of the research will be to examine whether providing dental treatment to pregnant mothers suffering from gum disease results in a decrease in premature births.
Professor Lucilla Poston, of Tommy's Campaign, the national pregnancy health charity, said: "This study indicates just how important it is for a mother to take care of herself throughout her pregnancy and attend regular dental checks as well as her antenatal appointments."
Dental treatment is free of charge in the UK throughout pregnancy and for the first year following a baby's birth.
A separate US study, earlier this year, led by Dr Marjorie Jeffcoat, of the Medical College of Georgia, found that women with any sort of periodontal disease may be up to seven times more likely to deliver a premature baby.
Other major risk factors for periodontal disease include genito-urinary infections, smoking and excessive alcohol drinking.
Professor Offenbacher will present his findings at a conference on "The Problem with Prematurity" on Monday.
The conference is part of National Pregnancy Week, organised by Tommy's Campaign.