When a baby is born, the first bacteria that it receives is from the birth canal- and this bacteria is responsible for beginning the bacterial colonization in the baby’s digestive system.
Stress has been proven to cause changes in the bacteria in the mother’s birth canal. In mouse studies, it was found that stressed, pregnant mice not only produced more types of bacteria, but Lactobacillus, a common and helpful bacteria for babies’ gut colonization, was greatly reduced. After birth, it was also found that gene expression in the brain was negatively affected by a reduced amount of Lactobacillus- specifically, genes related to neuron grown and connections in the brain.
Understanding this could lead to helpful therapies for human patients. By discovering the most useful bacteria to begin gut colonization, doctors can give newborns a dose of this beneficial bacteria after birth- this would be particularly helpful for babies born via C-section (who do not travel through the birth canal) and babies born to mothers who were on antibiotics (further altering the types of bacteria present).
So for pregnant moms out there- take it easy! Less stress for you ultimately means a healthier, happier baby.