Expectant mothers’ immune systems shape babies’ brains

A woman’s immune response to stress or pathogens during pregnancy shapes the way her baby’s brain develops, new research suggests.

Fighting off infections, stress and illness triggers an inflammatory response in the body that can change and even damage a fetus’s developing brain, a new study from Children’s Hospital Los Angeles and the University of Southern California indicates.

The researchers found the effects of this inflammatory response continued well into the toddler stage, potentially shaping the development of speech and motor skills as well as behavioral tendencies in the young children.

Though similar patterns have been seen in studies of animals, the new study is the first to document these changes in humans and may indicate that maternal health needs to be monitored even more carefully than previously thought.

Women’s immune system activity during pregnancy shapes the development of babies’ brains, new research suggests  

The conventional wisdom that healthy mothers make healthy babies has long been a rule of thumb for pregnant women, but the new study, published in the Journal of Neuroscience indicates an even closer correlation between the two than previously observed in humans.

During pregnancy, a woman’s body releases hormones that suppress the immune system.

A developing fetus is a new and foreign presence in the body, so these hormones have to make sure that the immune system does not attack a developing presence it does not recognize.

While this biological process makes it possible for women to carry to term, it also leaves them – and their developing babies – more vulnerable than usual to other invaders, like colds, flus, allergies and even stress.

Additionally, other recent research has suggested that when a pregnant woman does catch a virus like the flu, her immune system tends to have an over-exaggerated response to the invading trigger.

As the immune system deploys white blood cells, antibodies, chemicals and proteins to attack pathogens, the body experiences inflammation from the increase in these substances.

Previous animal studies have shown that the proteins in this response had some impact on offspring, but this has been difficult to study.

In the new research, the study authors were interested in examining inflammatory responses during the third trimester, which is the most important period of pregnancy for the development of the brain and its higher functions.

The researchers recruited expectant mothers between the ages of 14 and 19 whose young ages, they believed, would make them particularly likely to experience higher levels of stress than mothers in other age groups.

That stress can trigger the same type of inflammatory responses as illnesses, providing insights into how either external factor might impact a developing baby.

During the third trimester of the women’s pregnancies, the researchers took blood samples from them to check for proteins that would indicate their immune systems were activated, or had detected something they needed to fight (most likely, stress).

The researchers simultaneously tracked the heart rates of the fetuses as an indicator of their nervous system development.

They fetuses had more variable, inconsistent heart rates if their mothers had elevated levels of the immunity proteins in their blood, indicating a close link between the mother’s response to stress and the development of the fetus’s brain.

After the mothers gave birth, the researchers continued to assess the cognitive development of their babies.

Brain scans just after their births showed remarkable differences in the way sthe babies’ brains had developed.

The children of mothers who had had high levels of immune system activity during the third trimester were born with deficiencies in the ways certain regions of their brains communicated.

Specifically, the salience network of their brains, which instructs the rest of the nervous system what to pay attention to and when, was poorly connected.

‘Our brain is constantly receiving information from our bodies and the external world,’ said Dr Bradley Peterson, the study’s lead author and director of the Institute for the Developing Mind in the Department of Pediatrics at Children’s Hospital Los Angeles.

‘The salience network sifts through that information and decides what is important and warrants action,’ he explained.

Impaired functions of this network have also been linked to disorders such as schizophrenia and autism spectrum disorders.

Dr Peterson and his team continued to monitor the children, and found that even through the first 14 months of their lives, the babies whose mothers had had immune responses to stress did not develop language and motor skills in the same ways as the other babies.

‘This finding fills in a missing piece,’ Dr Peterson said.

‘Although studies in animals have suggested it, this 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,’ he explained.

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