A new study published in the Journal of Neuroscience revealed how a pregnant woman's activated immune system can impact the developing nervous system of infant. The researchers found that short- and long-term brain functioning can be influenced by immune system activity during the third trimester of gestation.

Many triggers can generate immune responses, such as infections, stress, illness, or allergies. When the body's immune system detects one of these triggers, proteins are released as part of an inflammatory response. Animal studies have shown that some of the proteins released during this response can impact offspring, but little is known about the effect on humans.

The study recruited young women in their second trimester and involved a blood draw and fetal heart monitoring during the third trimester, anatomical brain scans of the newborns, and cognitive behavioral assessment of the babies at 14 months of age. The ages of the pregnant young women (14 to 19 years) put them at high risk for psychosocial stress and resulting inflammation.

The research team led Bradley Peterson, director of the Institute for the Developing Mind in the Department of Pediatrics at Children's Hospital Los Angeles, followed babies from a critical point in fetal brain development in utero, through birth, and all the way into toddlerhood. The goal was to examine the possible link between markers of inflammation in the mother's blood with changes in the nervous system of their babies.

Blood drawn from mothers during their third trimester was tested for levels of IL-6 and CRP –  found at higher levels when the immune system is activated. Peterson's team also monitored fetal heart rate as an indicator for nervous system development. The team found that CRP did correlate with variability of the fetal heart rate indicating that maternal inflammation was already beginning to shape brain development.

Brain MRI during the baby's first week of life, revealed a striking finding – significant changes in the communication between specific brain regions correlated with elevated maternal IL-6 and CRP levels. These brain regions are known collectively as the salience network, whose job is to filter stimuli coming into the brain and determine which deserve attention.

"Our brain is constantly receiving information from our bodies and the external world," explains Peterson. "The salience network sifts through that information and decides what is important and warrants action." Disturbances in the functioning of this network, as well as various kind of infection and other triggers of a pregnant woman's immune response, have been linked to development of psychiatric illnesses.

The correlations of elevated maternal inflammatory markers were continued to persist into toddlerhood. When the babies turned 14 months of age, researchers assessed them for motor skills, language development, and behavior. Following the established Bayley Scales of Infant and Toddler Development-Third Edition, Peterson found significant changes in the scores of toddlers born to mothers with elevated levels of both IL-6 and CRP.

The present, "study indicates that markers of inflammation in a mom's blood can be associated with short- and long-term changes in their child's brain, which will now allow us to identify ways to prevent those effects and ensure children develop in the healthiest possible way beginning in the womb and continuing through later childhood and beyond," Peterson concludes.