Normal Oral Bacteria May be Linked to Preterm Births

Normal bacteria found in the mouth may infect the placenta, causing preterm labor and stillbirth according to researchers in the US.

Bacterial infection has long been linked with preterm and still births, but until relatively recently we assumed that the infections came from the vaginal tract.  Over the past few years, studies have linked periodontal disease to preterm birth.  Now New evidence suggests that even mom’s with healthy mouths are at risk.

Researchers injected pregnant mice with samples of human saliva and gingival plaque, and found that certain bacteria found in the samples were able to grow within the placenta.  This bacteria can cause an inflammatory reaction in the placenta which can lead to a variety of problems.  The bacteria isolated from the placenta included normal oral bacteria like Streptococcus, Leptotricia, Fusobacterium nucleatum and Veillenella.  This research is interesting because it shows that even women with good oral hygiene may be at risk of these potentially dangerous infections if they get a cut or inflammation in their mouth that allows oral bacteria to enter their blood stream.

While maintaining good oral hygiene is always a good idea, this study raises many questions in my mind.  If the results of this study are reproducible, I’m curious to see how it will impact oral care guidelines for pregnant women.  I know with my last two pregnancies, my health care provider said she recommended that all her patients have a dental cleaning early in the second trimester, after morning sickness subsided.  I also know that some dental hygienists are rougher or more aggressive than others while doing routine cleanings.  If a cut in an otherwise healthy mouth could introduce bacteria that were potentially harmful to the placenta into the bloodstream, it seems like getting your teeth cleaned or other non-emergent dental work done during pregnancy might not really be the best idea.

I’ll definitely be waiting to hear more reactions to this study and any follow up work that is done.


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  1. Sardini et al. Transmission of Diverse Oral Bacteria to Murine Placenta: Evidence for the Oral Microbiome as a Potential Source of Intrauterine Infection.  Infection and Immunity, April 2010, p. 1789-1796, Vol. 78, No. 4.  doi:10.1128/IAI.01395-09


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