Studies that followed the health of pregnant women and their babies suggest that inflammation caused by infections like flu can lead to changes in the child’s brain, and that these may affect their cognitive abilities later on.
The findings make it all the more important that pregnant women try to avoid infections, such as by getting vaccinated against flu and practising basic hygiene measures like hand-washing, says of the Children’s Hospital Los Angeles.
Some microbes can directly infect a fetus during pregnancy, and cause developmental problems – Zika virus, for example, appears to be able to infect brain cells in the womb. But there’s some evidence that maternal infections might also affect fetuses indirectly, by putting the woman into a state of heightened immune system activity. For instance, there is evidence that there is a higher rate of schizophrenia among people who were born .
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Some studies suggest flu may raise the likelihood of having a child who has schizophrenia from around 1 per cent , and infections have also been linked to autism, attention-deficit hyperactivity disorder and depression. But these studies are not conclusive and there has been debate about whether infections in pregnant women really do affect the brains of their children.
Brain changes
Research in animals including monkeys has shown infections during pregnancy can lead to brain changes in offspring, such as reductions in size of various parts of the brain. Injecting animals with molecules that the immune system uses to communicate can also affect the brain, which suggests the brain changes are caused by inflammation and the body’s immune response, not the pathogen itself.
To see if the same effect occurs in people, of Oregon Health & Science University in Portland and his colleagues followed 46 women from pregnancy through to early motherhood. During pregnancy, they measured levels of a signalling molecule called interleukin-6 in the women’s blood. This molecule is involved in the immune response to infections, and is a sign of inflammation.
The team scanned the children’s brains soon after they were born and gave them tests. Two years later, their memory was assessed using a game in which they had to remember where stickers were hidden among pots of different colours. The team found that infants who performed worse at the memory test had been born to mothers who showed signs of high inflammation during pregnancy.
The researchers also saw that these babies’ brains were different compared with those whose mothers had had less inflammation when scanned at 4 weeks old. They had different patterns of connections between several parts of the brain involved in memory, including in a network that is involved in paying attention to important things, known as the salience network.
Improved performance
But the picture isn’t clear-cut. In February, Peterson’s group reported a similar study, in which they followed . While they also found that higher inflammation in pregnancy was linked with altered brain connections in the salience network at a few weeks of age, this didn’t seem to have a bad effect. When tested at the age of 1, these infants actually had better cognitive abilities than those whose mothers had had less inflammation during pregnancy.
That might be because the fetal brain tries to compensate for the damage caused by inflammation in a way that strengthens some cognitive abilities, says Peterson. “If there’s a problem in one part of the system other portions kick in to try to right the ship,” he says.
While the contradictory results on cognitive performance may be hard to interpret, the fact that inflammation seems to lead to consistent changes in brain scans adds weight to the findings from animal and human population studies, he says.
As well as getting vaccinated against flu and practising good hygiene, Peterson suggests that pregnant women may want to wear face-masks if they need to spend time with someone who has a contagious illness. “We want to be careful not to create anxiety, but it’s better to keep your distance if you know someone is sick,” he says.
Journal reference: Nature Neuroscience, DOI: 10.1038/s41593-018-0128-y
