New York, Jun 2 (IANS): Even mild viral attacks such as the flu, which generally does not require a mother to visit the doctor, might affect the development of a baby's brain, new research suggests.

"In the first trimester of pregnancy, if the mom gets an infection such as the flu, the risk of the baby developing schizophrenia 15 years later is increased by approximately threefold," said study senior author Alexandre Bonnin, Assistant Professor at the Keck School of Medicine of University of Southern California in the US.

"It doesn't mean that if the mom has the flu, the kid will systematically have schizophrenia, but the risk is increased by threefold," he explained.

For the study, the researchers examined how the immune systems of pregnant mice (roughly equivalent to human mothers in their first trimester) reacted to a chemical that mimics a viral infection akin to the flu.

Babies born to mothers whose immune systems had to grapple with a viral assault -- even a mild one - had an increased risk of brain and central nervous system abnormalities, the findings showed.

The researchers found that the levels of tryptophan, an amino acid that activates the immune system, increased, causing the placenta to produce more serotonin, which led to higher concentrations of serotonin in the fetal brain.

"Serotonin is very important for fetal brain development and can modulate the way the fetal brain is wired," Bonnin said.

"In response to boosted serotonin levels coming from the placenta, the fetal brain stunted its own genesis of serotonin neurons, probably because receptors sensed there was too much serotonin in there. That can be a problem, especially when it leads to the front of the brain being not developed as much as it should be," he noted.

The study was published in The Journal of Neuroscience.

In this study, scientists administered a drug to inhibit the activity of an enzyme that produces serotonin via increased tryptophan levels.

They blocked excess serotonin production in the placenta, which appeared to normalise fetal forebrain development.