New research shows that neurological damage for babies who were exposed to the Zika virus while in the womb continues to unfold years after birth.
Developmental problems were found in one-third of the 216 children studied, some of whom were 3 years old. The problems affected language, thinking and motor skills development. Some also had eye and hearing issues.
Surprisingly, the researchers also discovered that fewer than 4% of the children had microcephaly -- a smaller-than-normal head that is one of the hallmarks of Zika exposure in the womb. And in two of those cases, the head actually grew to normal size over time.
"Children who were exposed to Zika during their mothers' pregnancy need to have developmental assessments over time, and eye and hearing exams should be performed," said lead study author Dr. Karin Nielsen-Saines. She is a professor of clinical pediatrics at the University of California, Los Angeles.
"If there is risk of developmental delay, or developmental delay is identified, there are cognitive, language and behavior interventions that can be put in place to improve outcomes for these children," she added in a university news release.
The finding that some children born with microcephaly went on to develop normal head circumference by age 1 means that "microcephaly is not necessarily static," Nielsen-Saines said.
The study was published July 8 in the journal Nature Medicine.
The researchers noted that they didn't have a comparison group of non-exposed children who were born at the same time and raised in the same settings as those known to have been exposed to Zika in the womb.
"Zika exposure can be a very difficult condition to diagnose in retrospect, so we can't rule out undiagnosed Zika infection in a control group of children enrolled at the same time," Nielsen-Saines said.
"Neurodevelopmental tests should be done simultaneously in similar populations with the same background," she suggested.
"These children require close attention and ongoing surveillance, so that prompt interventions to improve their development can be provided if needed," Nielsen-Saines said.
The U.S. Centers for Disease Control and Prevention has more on Zika.