Vaginal Microbiome Crucial to Development of Newborns

Scientists have previously hypothesized that exposure to a mother's vaginal microbiome during birth is a critical step in forming a newborn’s microbiome. Neonates birthed by cesarean-section miss out on this initial exposure and are more likely to be exposed to and their guts then colonized by other bacteria in the local environment, including the mother’s skin and potential pathogens in the hospital. However, recent studies have indicated that the pregnant microbiome and her children’s may be modulated by stress, according to a study published in Endocrinology.

Although we still believe the neonate’s gut relies heavily on the maternal vaginal microbiome, shifts throughout pregnancy stemming from stress have altered the initial vaginal microbiome and determined the host’s immune response that is established throughout this delicate period.

Stress alters the vaginal microbiome

The study included pregnant mice that underwent stress tests utilizing predatory odors, unfamiliar sounds or restraints. After birth, researchers analyzed the bacterial communities of the mothers’ vaginal fluids and the pups’ colons. Interestingly enough, the results indicated that stress throughout pregnancy may disrupt several proteins associated with vaginal immunity and levels of Lactobacillus. Not surprisingly, this was associated to lower instances of Lactobacillus found within the neonate’s guts.  Furthermore, male offspring from stressed mothers demonstrated increases in Bacteroidesin and Clostridium, anaerobic bacteria linked to dysbiosis.

These studies show enormous potential regarding the vaginal microbiome and birth, and how C-sections may potentially provide fewer benefits than natural birth to newborns. Some countries currently administer vaginal lavages orally to babies delivered by C-section to optimize exposure and increase immunity.

The research team calculated the free amino acids in the newborn brains to comprehend how they were influenced by the microbiome.  Specific amino acid levels were observed to be reduced in male developing brains; however, this was not seen in female newborns. More research is required to understand the mechanisms behind the clear sex-specific effects and the link between the pregnant microbiome and newborn brain metabolism.


Jasarevic, E, Howerton, C et al. Alterations in the vaginal microbiome by maternal stress are associated with metabolic reprogramming of the offspring gut and brain. Endocrinology. 2015. 159:9; doi:

Keneer, Amanda. "Pregnancy Stress Can Affect Offspring’s Microbiomes." Scientist. 2015. <>

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