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TORONTO -- Babies exposed to Zika virus in utero but who are born with normal neuroimaging appear to develop in much the same way as do unexposed infants, a researcher said here.
At 6 months of age, the infants had neuromotor skills similar to those of unexposed controls, according to Sarah Mulkey, MD, of Children's National Health System in Bethesda, Md.
And a difference seen on one test is likely the result of culture rather than biology, Mulkey said at the annual meeting of the Pediatric Academic Societies.
"This is really a major question we want to be able to answer for mothers and fathers" of infants exposed to Zika but born apparently normal, she said: "Is that baby going to stay OK?"
The early evidence is promising, Mulkey said, adding the evaluation is continuing.
The finding is "potentially very good news," commented Paul Spearman, MD, of Cincinnati Children's Hospital Medical Center, who was not part of the study but who co-moderated the session at which it was presented.
But, he told MedPage Today, the investigators need to figure out how their work compares with studies from other parts of the world, where "there have been observations that are more concerning" in babies who have appeared normal at birth.
But, he added, "it's very positive news if it can be validated."
Zika is a flavivirus, a cousin of yellow fever, dengue, and chikungunya, all carried by mosquitoes. Most adults infected with Zika virus are asymptomatic or have mild symptoms including fever, headaches, joint pain, rash, and conjunctivitis, but a small proportion develop Guillain-Barré Syndrome.
While it has been known for many years, Zika burst into prominence in 2015 in South America, when experts linked infection in pregnant women with serious neurological and ocular abnormalities -- most notably microcephaly -- in their infants exposed in utero.
But not all fetuses exposed develop such symptoms and Mulkey and colleagues are following about 36 infants in Columbia and Washington DC whose mothers had documented Zika virus during their pregnancies, but whose babies appeared normal both on prenatal and postnatal neuroimaging.
For this analysis, the infants were scored on two tests -- the Alberta Infant Motor Scale (AIMS) and the Warner Initial Development Evaluation of Adaptive and Functional Skills (WIDEA) -- and compared with 68 normative control infants.
On the observational AIMS test, Mulkey said, the average score was 24.8, which was not different from the control cohort.
The WIDEA test has four domains -- mobility, self-care (such things as feeding, dressing, and diaper awareness), communication, and social cognition. The latter two domains were not relevant at 6 months, since those skills appear later in life, Mulkey noted, so only the first two were studied.
The average WIDEA score was significantly lower for the Zika-exposed infants -- 54.8 versus 65.1 -- but the difference was driven by the self-care domain, Mulkey said. In that domain, the Zika-exposed babies averaged 21.6 versus 24.6 for the control infants.
On the other hand, there was no difference on the mobility domain, she reported.
The self-care difference, she said, is likely a matter of culture rather than a "true delay" and an evaluation where the controls were Colombian babies might not have shown any variation. "I feel if there was true delay we would have seen a difference in the motor skills of these babies as well," Mulkey said.
The infants are now being evaluated as they reach their first birthday, she added.