"Our results encourage young women of fertile age to take care of their oral health and attend periodontal evaluations regularly," said one of the researchers Susanna Paju of the University of Helsinki in Finland.
Periodontal (gum) disease is an inflammatory reaction to a bacterial infection below the gum line.
The study involved 256 healthy non-pregnant women (mean age 29.2 years, range 19 to 42) who had discontinued contraception in order to become pregnant.
They were enrolled from the general community from Southern Finland.
Participants were followed-up to establish whether they did or did not become pregnant during the observation period of 12 months.
Porphyromonas gingivalis, a bacterium associated with periodontal diseases, was significantly more frequently detected in the saliva among women who did not become pregnant during the one-year follow-up period than among those who did, according to the study published in the Journal of Oral Microbiology.
The levels of salivary and serum antibodies against this pathogen were also significantly higher in women who did not become pregnant.
Statistical analysis showed that the finding was independent of other risk factors contributing to conception, such as age, current smoking, socioeconomic status, bacterial vaginosis, previous deliveries, or clinical periodontal disease.
Women who had P. gingivalis in the saliva and higher saliva or serum antibody concentrations against this bacterium had a three-fold hazard for not becoming pregnant compared to their counterparts.
Increased hazard was nearly four-fold if more than one of these qualities and clinical signs of periodontitis were present.
"Our study does not answer the question on possible reasons for infertility but it shows that periodontal bacteria may have a systemic effect even in lower amounts, and even before clear clinical signs of gum disease can be seen," Paju said.
"More studies are needed to explain the mechanisms behind this association," Paju noted.
Young women are encouraged to take care of their oral health and maintain good oral hygiene when they are planning pregnancy, said Paju.