Researchers have discovered why influenza can lead to life-threatening complications during pregnancy. In most people, influenza stays in the upper respiratory tract—mainly the nose—and clears without spreading further. But during pregnancy, the virus can extend beyond the lungs into the cardiovascular system, increasing the risk of severe complications for mothers and babies.
In a new study, published in Science Advances, researchers identified a viral sensor in the immune system, known as TLR7, that can become overactive during pregnancy, amplifying inflammation and spreading disease into the bloodstream. Blocking TLR7 could help protect developing babies by stopping the placenta from becoming overly inflamed during flu infection.
“The findings shift understanding of how respiratory viruses affect pregnancy, showing that harm is not caused by the virus directly reaching the fetus, but by an overactive maternal immune response that disrupts vascular function,” said lead author Stella Liong from RMIT’s School of Health and Biomedical Sciences.
Earlier studies have shown that severe flu in pregnancy can have long‑term impacts on babies’ brain development, by inflaming blood vessels and reducing the flow of oxygen and nutrients from mother to baby.
This new study pinpoints the underlying cause of that damage, reshaping understanding of flu‑related risk in pregnancy and opening the door to more targeted therapies.
“With this new information, we can start to work out how to switch off this TLR7 sensor, which could help prevent the harmful inflammation that makes flu in pregnancy so dangerous,” said Liong.
RMIT co-lead author Stavros Selemidis said future treatments could focus on the immune system rather than the virus itself.
“We’re ready to work with partners to help develop the next generation of therapies and clinical guidelines,” he said.
The team is planning further research on how to target TLR7 to reduce the risk of severe influenza and pregnancy complications.
Data from RMIT University