A new study suggests that the presence a Zika infection in a newborn may increase the risk of having birth defects.
Researchers from the University of California at Berkeley found that the more time a mother has been exposed to Zika virus in utero, the higher the risk her child will develop birth defects, including microcephaly.
They analyzed data from more than 5,000 women from the California state Department of Public Health and Environment, which has tracked birth defects for over a decade.
They found that babies born to mothers who had been exposed during the first three months of pregnancy to Zika were more likely to have microcephelias and other birth defects compared with babies born during the same period to mothers that had never been exposed.
Microcephals are tiny, often malformed, head and neck deformities that are difficult to diagnose and treat.
A typical birth defect is a smaller head with an abnormal neck or spine, as well as birth defects like microcepsy, where a baby’s head is slightly off center.
In babies born with microcephalies, the head and spine are usually normal, and the head usually looks more like that of a toddler.
While there has been some concern about Zika’s potential to cause birth defects and other health problems in babies, the study was the first to suggest that this was true in a birth cohort of more than 1,000 people from the state.
The researchers said that the findings do not mean that the Zika virus causes microceperias.
They also found that exposure to Zika at different times during pregnancy may not have affected birth outcomes, or whether the babies born after exposure would be born with birth defects at all.
“It’s not clear that Zika virus is a risk factor for microcepheias,” said Dr. Elizabeth Kroll, an associate professor of pediatrics at the University at Buffalo and a co-author of the study.
“It could be a risk for some birth defects that may not show up until later in life, but we still don’t know what that means.”
The researchers did not include the infants born with Zika during the study because the state had not tracked those babies.
The researchers also did not have data on how long the mothers had been infected before becoming pregnant or on the children’s birth outcomes.
A large study of more that 100,000 babies born in the U.S. between January and March 2017 found that there was no link between the virus and birth defects among babies born before their first birthday.
That study, which was published last month in Pediatrics, also found no link to microcepsias or other birth defect outcomes.
The authors of that study, Dr. Jeffrey F. Meyer and Dr. Matthew H. Stolaroff, also said that they were unaware of any birth defects caused by Zika, which is now thought to be circulating only in Africa and Asia.
Dr. David Eisenberg, a pediatrician and researcher at Children’s Hospital of Philadelphia, said that while the new study is important, the findings were not enough to be considered definitive.
“I would still urge people to discuss any concerns about Zika with their doctor before they get pregnant,” he said.
“We do not know all the possible risks and benefits.”