Exposing newborn male mice delivered by C-section to vaginal microbes from stressed female mice causes physiological changes that partially resemble those seen in the male offspring of mice that were stressed during pregnancy, reports a study published online this week in Nature Neuroscience. This finding may pave the way to a better understanding of how maternal stress impacts development.
Microbes present in vaginal fluids colonize the guts of mouse pups during birth, and the composition of the gut microbiome influences the brain’s response to stress later in life. In mice, prenatal stress is known to alter the vaginal microbiota and affect male offspring’s brain function after birth, but it was not clear whether the latter is a consequence of the microbiota changing.
Tracy Bale and colleagues transplant microbes from the vaginal fluids of either stressed or unstressed pregnant mice into both prenatally stressed and unstressed male pups shortly after birth by C-section. They observe changes in body weight, gut microbiota and stress hormone levels in pups exposed to both stress in the womb and microbiota from stressed mothers at birth. The authors find that these effects can be partially reproduced in unstressed, new-born male pups by transferring vaginal microbes from stressed mothers. Microbes from unstressed mothers, however, could not offset the effects of stress in the womb. These findings in mice indicate that stress during pregnancy affects pups both directly during their gestation, and indirectly by altering the vaginal microbiota of the dam. In humans, maternal stress during pregnancy is a risk factor for psychiatric disorders in offspring, but it remains unclear whether this risk is also influenced by the vaginal microbiota.