Microbes present in the saliva of pregnant women differ according to whether they are experiencing life stress and symptoms of anxiety, depression and post-traumatic stress disorder.

The study — published in the open access journal BMJ Mental Health — is the first to look at the association between the type and number of microorganisms in the mouth and throat, also known as the oral microbiome, and maternal mental health.

The study included 224 pregnant women enrolled in the Michigan Prenatal Stress Study who were assessed for recent stresses and mental health symptoms during their second trimester. Women were asked to provide saliva samples during the week of their assessments. The results showed the oral microbiome varied based on whether women had reported symptoms of life stress, anxiety, depression or post-traumatic stress disorder, also called PTSD, during the assessments.