Biomarkers associated with severe birth defects in babies born to women infected with the Zika virus have been identified, a discovery that could lead to screening tests and a better understanding about how the infection leads to fetal abnormalities, USC researchers announced Friday.

“The highest risk of birth defects is from Zika virus infection during the first and second trimester,” said the study’s first author, Suan-Sin Foo, a research associate in the Department of Molecular Microbiology and Immunology at the Keck School of Medicine of USC. “A prenatal test has the potential to relieve the concerns of many expectant mothers. We still have a lot to learn about how Zika virus affects the immune responses in the mother, and how infection can negatively impact her baby.”

Most people infected with the Zika virus, spread by the Aedes mosquito, experience no symptoms or mild illness with low-grade fever. But fetuses exposed to Zika in the womb are at risk for devastating neurological defects.

One of those defects, microcephaly — a smaller-than-usual head size — gained prominence in 2015 with Brazil reporting an unusual number of cases in babies born to mothers infected with the virus, according to USC.

As those infants have become toddlers, some can’t see, walk, chew or talk and will require a lifetime of care, according to the U.S. Centers for Disease Control and Prevention. In the United States, there have been 2,483 pregnant women infected with Zika and 116 infants born with Zika-associated birth defects since 2015.

Aedes mosquitoes have been found in Los Angeles, but none carrying the Zika virus, according to the Los Angeles County Department of Public Health.

For the study, researchers examined the immune systems of pregnant women through blood samples taken during the first, second and third trimesters of pregnancy. They compared blood samples from 30 Zika-infected, pregnant women in Brazil with 30 healthy pregnant women in Brazil and 14 in Los Angeles.

The findings appear in the Nov. 2 Journal of Clinical Investigation Insight.

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