Prenatal Stress Alters Bacterial Colonization of the Gut in Infant Monkeys

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Abstract
The hypothesis that prenatal stress lowers the levels of protective microflora and increases the risk for postpartum Gram-negative pathogens was tested in infant monkeys. Female monkeys were left undisturbed or were stressed during pregnancy using an acoustical startle paradigm for 6 weeks either early or late in their 24-week gestation. Several types of intestinal microflora were repeatedly enumerated by fecal culture while infants were reared normally by their mothers. Significant changes in microflora concentrations occurred during the first 6 months of life. The profile of total aerobes and facultative anaerobes was biphasic, with peak concentrations occurring between 2 and 16 weeks of age. The numbers of bifidobacteria and lactobacilli were low at 2 days after birth but rapidly increased to a peak between 8 and 16 weeks of age. Although similar temporal patterns were evident in all infants, prenatal stress reduced the overall numbers of bifidobacteria and lactobacilli. Moderate disturbance during pregnancy was sufficient to alter the intestinal microflora in the newborn infant. These alterations could result in enhanced susceptibility to infection and suggest a mechanism for some effects of maternal pregnancy conditions on infant health.