Exposure to maternal cortisol during the third trimester is beneficial to a child’s cognitive function later in life, according to a study recently published in Psychoneuroendocrinology.

The human brain undergoes a complex series of events in its journey from embryo to adult. Developmental stages are influenced by early environmental conditions including in utero experiences. However, the neurodevelopment that occurs during the foetal period is far greater than any other period in an individual’s life and the stage at which the brain is most vulnerable to the environment.

Cortisol, a hormone that regulates a wide range of bodily processes, is said to be crucial for healthy foetal brain development. Cortisol influences various stages of foetal neurodevelopment including neurogenesis, axonal development and myelination. The effects of cortisol are largest in areas of the brain that contain the most cortisol receptors such as the amygdala, hippocampus and prefrontal cortex (PFC).

The study conducted by a team led by Elysia Davis (University of Denver) recruited a total of 91 mother-child pairs and measured the mother’s cortisol levels at 19 and 31 weeks during the pregnancy. At age 6-9 years the children were tested for cognitive function using a range of standardized measures. MRI scans were used to examine the extent of cortical thickness in the children.

The results showed that children who experienced higher maternal cortisol levels during the third trimester displayed increased cortical thickness in frontal areas of the brain. High levels of maternal cortisol were also associated with improved cognitive function in children. The relatively high level of cortisol receptors in frontal regions of the brain is consistent with the finding that cortical thickness in children is increased with exposure to higher levels of maternal cortisol, suggesting that cortisol promotes foetal brain maturation.

Although, it appears that there is an ‘optimum concentration’ for cortisol, as extremely high levels of are thought to be toxic to the developing brain of a foetus. The authors state that the findings are ‘consistent with the role that cortisol plays in maturation of the human foetus.’

Overall, the findings suggest that higher levels of maternal cortisol during the third trimester is beneficial to neuro-cognitive development in children.