Scientists have grappled with the puzzle of autism’s origins for decades – now a study suggests a bad cold or flu during pregnancy could be a cause.
They’ve shown that when the mother’s immune system is ramped up in response to a viral infection, it can stunt the development of the growing baby’s brain.
Female embryos seemed protected from these effects, but one third of male embryos were impacted to some degree, according to the research on mice.
This aligns with the fact that autism is more prevalent in boys than girls, said the team from Cold Spring Harbor Laboratory (CSHL) in New York.
Researchers have found that autism could develop while a fetus is in the womb. When a pregnant woman gets a severe cold or flu, her immune response could cause a neurological reaction in the baby’s brain
Researchers simulated a viral infection in mice and tracked the fetus’ reaction to how the mom’s immune system responded to a cold or flu virus, known as maternal immune activation (MIA).
MIA is activated when the immune system kicks into high gear, increasing the levels of cytokines and chemokines which can cross the placenta and baby’s blood-brain barrier.
Chemokines fight the flu by moving other immune cells, like cytokines, to the site of the infection.
Cytokines are small immune cells that fight off harmful pathogens by summoning other immune cells through creating symptoms like fever, runny nose and body aches.
Because a fetus’ brain is so sensitive to environmental signals in the womb, this reaction can cause a wide range of behavioral issues including social impairments like autism spectrum disorder.
Irene Sanchez Martin, a postdoctoral student at CSHL, said that her recent experiments with mice showed that when the mother contracted a virus, the embryo’s brain development slowed.
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‘The difference in my work is that I check what happened to the fetus’ 24 hours after exposure to maternal inflammation, rather than analyzing the behaviors of the offspring as adults.’
Sanchez Martin focused on how prenatal inflammation caused by the cold or flu impacted the developing fetus’ brain.
Prenatal inflammation has been linked to causing dysfunction in the growing fetus’ brain and can impact how it organizes the neural networks which connect cells and synapses.
If these are disrupted, the number of neurons and synapses in the brain can decrease which has been connected to people developing autism.
One of the most major breakthroughs showed that although female embryos appeared to be protected from the MIA, about one-third of male embryos showed signs of a brain development deficit that was consistent with autism.
Autism is on the rise in the US, with an estimated one in 36 eight-year-olds diagnosed in 2020 compared to one in 150 in 2000
Additional research still needs to be conducted to unravel the connection between the immune system’s reaction to a virus and how it impacts the fetus.
More than 5.4 million people in the US are currently diagnosed with autism and 40 to 80 percent are likely related to genetics, but that still means 20 to 60 percent are caused by other factors.
Diagnosing early is crucial in autism because there are currently no treatments, and it takes years to test and diagnose the disorder.
Sanchez Martin said her research is still in the early stages and more needs to be conducted to definitively link cold and flu viruses to autism.
However, she is hopeful that future findings could help doctors recognize the early warning signs of autism before a child is born.
Autism among children is on the rise throughout the US, with the Centers for Disease Control and Prevention (CDC) reporting that in 2000 an estimated one in 150 eight-year-olds had autism.
But by 2020 that number had skyrocketed to one in 36 eight-year-olds having autism.
The increase could be attributed to physicians getting better at identifying cases of autism and more awareness surrounding the disorder.