Cognition Mostly Normal in Infants With Prenatal Zika Exposure but Without Microcephaly

By Will Boggs MD

November 05, 2019

NEW YORK (Reuters Health) - Cognitive development of infants with prenatal exposure to Zika virus but without microcephaly is similar to that of unexposed infants, according to a study of Puerto Rican infants.

"There were two things that we found surprising," Dr. Charles A. Nelson III from Boston Children's Hospital and Harvard Medical School told Reuters Health by email. "First, that the effects were limited to receptive language, and second, that even here the effects were quite modest."

Prenatal infection with Zika virus has been associated with abnormalities in brain structure (e.g., microcephaly) and various health impairments early after birth. Whether prenatal exposure to the virus affects physical and cognitive development over the first year of life remains unclear.

Dr. Nelson and colleagues examined whether there is an association between Zika virus status and cognitive, language and motor development in their study of 65 infants, including 29 exposed to Zika virus and 36 not exposed, whose mean age at the time of cognitive testing was 8.98 months.

Overall cognitive scores did not differ significantly between infants whose mothers tested positive or negative for Zika virus, the researchers report in JAMA Network Open, online October 25.

Moreover, the groups did not differ in the fine-motor, expressive-language, visual-reception, or gross-motor development domains.

In contrast, infants exposed to Zika virus had significantly lower scores in the receptive-language domain, compared with infants not exposed to Zika virus.

In multivariable analyses, exposure to Zika virus was independently associated with lower receptive-language scores.

The study was conducted eight months after Hurricane Maria made landfall in Puerto Rico, and multivariable regression analysis also identified days without water as a significant contributor to lower receptive-language scores.

Other factors, ranging from parental education level to socioeconomic status to maternal anxiety, depression and perceived stress, were not significantly associated with cognitive outcome.

"The fact that effects were a) limited to receptive language and b) overall quite modest gives us pause in thinking that infants infected with the Zika virus are across the board seriously impacted," Dr. Nelson said. "But, also keep in mind that none of our infants had microcephaly, I would argue that such infants are completely different than those we studied."

"Future research should aim to replicate these findings in larger samples and new contexts," the researchers note. "Additional studies should also examine these associations beyond the first year of life to determine whether the association with receptive language is observed and whether there are associations with other domains later in development."

"It would be ideal to see these infants as they get older, although I doubt we will have that opportunity," Dr. Nelson said.


JAMA Netw Open 2019.