Pregnant women, like everyone, get sick. And like everyone else, their bodies try to fight infection and, importantly, keep it from reaching the growing fetus.
If the mother’s immune system successfully defeats the virus before the developing baby is exposed or if the virus never crosses the placenta, is harm averted?
Counterintuitively, this protective response may be a risk factor for some neurological conditions in the baby later on.
This is the question that researchers, including me, have been probing at the neurodevelopment lab at the University of California, Davis. Research suggests that the mother’s defensive immune response to an infection, for instance, alone is sufficient to cause lifelong changes in brain architecture and function and in behavior in the offspring. This response is a strong risk factor for brain disorders like autism and schizophrenia.
Kimberley McAllister, who leads the neurodevelopment lab, and I reviewed recent research about what is called maternal immune activation (MIA) in humans and in animals in an article published today in Science. So what do we know so far about MIA and where research is headed?
What is maternal immune activation?
Maternal immune activation refers to the mother’s immune system defensive response to invading pathogens. During pregnancy the immune system changes to accommodate the needs of the growing fetus. These changes are complex and depend on her stage of pregnancy and the pathogens she encounters. The intensity of the immune response is highly individualized and represents a complex interaction between the mother’s genes and environment.
A study in humans has suggested that the degree and duration of MIA determines the risk of a child being diagnosed with a brain disorder later on, like autism or schizophrenia. And infections aren’t the only cause of MIA. For example, an increased risk is also associated with psychological stress during pregnancy, which triggers a similar immune activation.
Studies like these identify associations, but not causation. However, animal studies support a causal role for these risk factors and are beginning to reveal the underlying mechanisms.
Ultrasound image via www.shutterstock.com.