Most pregnant mothers will go to great lengths to avoid being sick, and science suggests that their concerns may be well founded.

Researchers have gained new insights into how maternal infections during pregnancy can lead to developmental disorders in children. According to a study in mice published on June 1, 2016 in The Journal of Neuroscience, infections in the mother cause inflammation that leads to changes in neural connections in the fetal brain, increasing the risk of disorders, such as autism, schizophrenia, and cognitive delays.

Somewhat ironically, the culprit is the inflammation that our immune system uses to fight off invading germs. Although it protects us from infection, inflammation in pregnant women affects the fetus, even when the fetus is uninfected. Recent research has shown that maternal viral infections like the flu and H1N1 (“Swine flu”) are associated with increased risk of autism spectrum disorder and schizophrenia developing in children after birth.

In pregnancy, maternal inflammation leading to elevated serotonin in the fetal brain may raise risk of developmental disorders. Tweet →

In their new paper, a team led by Alexandre Bonnin, Ph.D., a 2007 and 2010 NARSAD Young Investigator grantee and 2011 Freedman Prizewinner, provides insight into how such developmental disorders arise.

They used pregnant mice to study how inflammation affects fetal development, injecting the animals with a substance that induces an inflammatory response in the mother, mimicking the effects of a moderate infection.

The scientists noted an increase in the amount of a chemical known as tryptophan in the placenta. Tryptophan is a building block used to synthesize many molecules in the body, including a chemical messenger known as serotonin. Serotonin relays signals between neurons and helps establish the neural connections that are essential for healthy brain function. Altered levels of serotonin have been linked to brain disorders including depression and bipolar illness.

Dr. Bonnin and colleagues found that along with elevated levels of tryptophan, inflammation increased the production and activity of the protein that converts tryptophan to serotonin in the placenta. They discovered that the changes in the placenta caused a sustained increase in the amount of serotonin in the fetal brain.

The elevated serotonin levels, in turn, caused dramatic changes in neural connections in the fetal mouse brain, blunting the growth of projections that are required for normal function in adult animals. The scientists are now using these insights to further explore the early developmental origins of mental disorders.

Takeaway: Researchers have gained new insights into how the brain of an unborn child changes in response to inflammation in the mother, putting the child at risk for developmental disorders later in life. The scientists found that in pregnant mice, maternal inflammation causes an increase in the chemical messenger serotonin in the fetal brain, altering neural connections in the developing animal.