Fever in pregnancy may cause heart, facial defects in babies

Fever during the first three to eight weeks of pregnancy can cause the baby to develop heart and facial deformities, a study has found.
Researchers have known for decades that fevers in the first trimester of pregnancy increase risk for some heart defects and facial deformities such as cleft lip or palate.
It was debated whether a virus or other infection source causes the defects, or if fever alone is the underlying problem.
Scientists now have evidence indicating that the fever itself, not its root source, is what interferes with the development of the heart and jaw during the first three to eight weeks of pregnancy.

The findings, published in the journal Science Signaling, suggest a portion of congenital birth defects could be prevented by lowering the mother's fever with the judicious use of acetaminophen during the first trimester.
"While doctors advise most women to avoid any drug during pregnancy, there may be benefits to taking acetaminophen to reduce fever. Women should discuss all risks and benefits with their doctors," said Eric Benner, assistant professor at Duke University in the US.

Nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen and aspirin also reduce fevers, but some NSAIDs are not safe to use during the later stages of pregnancy.

There is also ongoing debate over whether sustained use of acetaminophen is safe during pregnancy to manage ongoing conditions such as arthritis, Benner said.
"However, its judicious use for an acute problem such as fever is considered safe. These findings suggest we can reduce the risk of birth defects that otherwise could lead to serious health complications requiring surgery," he said.
To observe how fever impacts a developing foetus, the researchers studied zebrafish and chicken embryos. They found that neural crest cells - cells that are critical building blocks for the heart, face and jaw - contain temperature- sensitive properties.

"We found that these neural crest cells contain temperature-sensitive ion channels that typically are found in your sensory neurons," Benner said.
"They're the channels that, when you stick your hand in a hot cup of water, tell your body the temperature has changed," he said.
Researchers engineered a non-invasive magnet-based technology to create fever-like conditions in two specific temperature-sensitive ion channels called TRPV1 and TRPV4 in the neural crest cells involved in developing the heart and face.
When those neural crest cells were subjected to conditions mimicking a transient fever, the embryos developed craniofacial irregularities and heart defects, including double outlet right ventricle, Tetralogy of Fallot and other outflow obstructions.

The type of defect depends on whether the fever occurs during heart development or head and face development. What researchers still do not know is whether or how the severity or duration of a fever impacts development, Benner said.