A new international study suggests that changes in a mother's body caused by stress during pregnancy may have a subtle effect on how her baby's brain develops. Some biological pathways are more vulnerable in male foetuses than in female foetuses. 

Dr Brian Kalish, a neonatologist at Boston Children's Hospital in the United States, led the study. It was published on Tuesday in the journal Nature Neuroscience. It looks at how stresses during pregnancy, especially changes in gut health and immune responses, affect the brain development of the baby that is still inside the mother. 

The gut–immune axis is what the work is mostly about. Simply put, this implies a close connection between the gut bacteria and the immune system. Both systems go through significant changes during pregnancy. When they are messed up by stress, an infection, or inflammation, those signals may get to the brain of a growing foetus. 

It has already been shown that changes in a mother's immune system make her child more likely to have neurodevelopmental problems, Dr Kalish said. "Our study sets up a detailed spatial transcriptomic resource of immune gene networks at a key time in the development of the embryonic brain." 

Researchers used advanced imaging and genetic mapping methods on mouse models to make a detailed picture of the area in the foetus's brain where immune-related genes are active in the middle and late stages of pregnancy. This let them see how immune messages caused by stress affect brain cells at a time when the brain is still developing quickly and is very sensitive. 

A response based on gender was one of the most important results. The CXCL12/CXCR7 pathway demonstrated a higher susceptibility of male foetal brains to immune system damage. This pathway helps young brain cells move to the right place and develop properly. In everyday terms, it's like a GPS. Getting rid of this information could mess up the way the brain normally wires itself. 

The experts want to make it clear that this finding does not mean that stress during pregnancy directly leads to brain problems. Instead, it shows how the surroundings before birth can affect the risk of development. 

"As a neonatologist, this work helps us learn more about environmental factors in early life that may affect neurodevelopmental potential and gives us ideas for how to help," Dr Kalish said. 

The results are important for public health because they show how important it is to help pregnant women's mental and physical health. Even though more research needs to be done on people, this study makes it possible to find risks earlier and maybe start preventative care before or soon after birth. 

Experts say that normal stress management, medical care, and nutritional support are still crucial for women who are expecting. The study sends a clear and strong message: what happens in a mother's body during pregnancy can have long-lasting effects on the growing child.