The greatest risk of Zika-associated infections occurs in pregnant women and their unborn children, as exposure to the virus in utero can cause microcephaly
, developmental delays, and other problems. But not all infants exposed to Zika virus in the womb develop related birth defects, according to a new study that presents a reliable estimate of the frequency of neurodevelopmental, vision, and hearing defects in infants and toddlers who were exposed to Zika before birth.
Since 2015, a total of 2490 pregnant women in the United States
and the District of Columbia have had laboratory evidence of possible Zika infection, and 116 liveborn infants had Zika-associated birth defects, according to data from the US Centers for Disease Control and Prevention.
Investigators recently discovered certain biomarkers in the blood of pregnant women with Zika
, which are associated with several fetal abnormalities. Now, new research published in the New England Journal of Medicine
offers a look at the rates of severe abnormalities and problems with motor skills and cognitive development in Zika-exposed infants aged 12 to 18 months.
The study includes findings from a longitudinal cohort of 131 infants who were enrolled upon the mother’s diagnosis with Zika during pregnancy via a positive molecular test that identified the virus in her blood or urine.
By the time the infants were 12 to 18 months old, the investigators identified significant problems in 7 of the 112 children (6.25%) evaluated for eye abnormalities, 6 of the 49 children (12.2%) evaluated for hearing problems, and 11 of the 94 children (11.7%) evaluated for severe delays in language, motor skills, and/or cognitive function, who also underwent brain imaging tests. A total of 16% of infants who had abnormal brain images went on to have normal cognitive, language, and motor skills by 12 to 18 months, while 2% of infants with normal scans went on to have severe developmental impairment in the second year of life.
In total, 14.5% of infants in the cohort had a severe developmental delay of 2 standard deviations below normal in motor, language, or cognitive function or had visual or hearing abnormalities.
“This does not include children with moderate impairment, which also need to be followed over time," sudy co-author Karin Nielsen-Saines, MD, a professor of clinical pediatrics in the Division of Infectious Diseases at University of California – Los Angeles Children’s Hospital, told Contagion®.
“This informs the public that Zika in pregnancy is not an all or nothing phenomenon. There are gradients of disease and very adverse events occur in at least 15% of children. Children exposed to Zika need to be followed over a longer period of time and may benefit from targeted developmental interventions such as stimulation and physical therapy to improve their developmental function.”
Dr. Nielsen-Saines noted that the team will continue to follow the cohort of Zika-exposed infants and will be reporting results on neurodevelopment from a larger group of infants in the near future but will not necessarily correlate functional findings with brain-imaging results.
“It’s reassuring that 85% of children did not have severe impairment in development or in visual and hearing deficits, but we need longer term follow-up to see how children will perform in school and what happens to those who had moderate degrees of impairment,” Dr. Nielsen-Saines told Contagion®.
She also pointed out that, in this cohort of children, investigators have seen an association between earlier infection during gestation and more severe developmental delay, a topic to be addressed in a future paper.
“The other important factor to consider is that not all Zika-exposed babies are necessarily infected with the virus, and this might be the reason we don’t see overwhelming rates of abnormalities. Diagnosing infection is more complicated however, so we need to follow exposed babies and evaluate their brain function over time in order to intervene if a problem is recognized,” Dr. Nielsen-Saines concluded.
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