The state of a woman's immune system during pregnancy may shape the connectivity of her child's brain, suggests a study, emphasising the influence of maternal health on a child's susceptibility to psychiatric disorders later in life.

The findings showed that short and long-term brain functioning can be influenced by immune system activity during the third trimester of gestation. Infections, stress, illness, or allergies are commonly known to trigger immune responses. When the body's immune system detects one of these factors, two proteins namely IL-6 and CRP are released as part of an inflammatory response.

The researchers found that higher maternal levels of these proteins were associated with greater connectivity of the infants' brain regions in this network and with higher cognitive ability at 14 months of age. "Our brain is constantly receiving information from our bodies and the external world," said Bradley Peterson, Director at Children's Hospital in Los Angeles -- a non-profit.

"The salience network sifts through that information and decides what is important and warrants action," Peterson added. The activation of the maternal immune system was also associated with lower foetal heart rate at the end of gestation, which may indicate delayed development of the autonomic nervous system. These results suggest that the final weeks of pregnancy have an important influence on a child's brain development, the researchers said.

For the study, published in the Journal of Neuroscience, the team recruited young women in their second trimester and involved a blood draw and foetal heart monitoring during the third trimester, along with anatomical brain scans of the newborns, and cognitive behavioural assessment of the babies at 14 months of age. Blood drawn from mothers during their third trimester was tested for levels of IL-6 and CRP.