Among pregnant women with polymerase chain reaction assay-confirmed, symptomatic Zika virus (ZIKV) infection, birth defects possibly linked to ZIKV were present in 7% of fetuses and infants, according to the results of a prospective cohort study ( identifier: NCT02916732) conducted in French territories in the Americas and published in The New England Journal of Medicine.

Between March 2016 and November 2016, pregnant women were enrolled in this analysis, which included all data collected up to April 27, 2017. Of the 555 fetuses and infants from the 546 pregnancies analyzed, 28 were either not carried to term or were stillborn and 527 were born alive.

Neurologic and ocular defects that were possibly associated with ZIKV infection were reported in 39 fetuses and infants (95% CI, 5.0-9.5). Among these, 10 were not carried to term because the pregnancy was terminated for medical reasons, 1 was stillborn, and 28 were live born.

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Microcephaly was observed in 32 fetuses and infants, of whom 9 had severe microcephaly (ie, head circumference >3 standard deviation units below the mean). Neurologic and ocular defects occurred significantly more often when ZIKV infection occurred in the first trimester (12.7% [24 of 189 fetuses]) than when ZIKV infection occurred in the second trimester (3.6% [9 of 252]) or the third trimester (5.3% [6 of 114]; P =.001).

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The investigators concluded that among pregnant women with ZIKV infection, birth defects were reported more often in fetuses and infants whose mothers had been infected with the virus early in their pregnancies. Longer-term follow-up is warranted to evaluate any late-onset manifestations not observed at birth.


Hoen B, Schaub B, Funk AL, et al. Pregnancy outcomes after ZIKV infection in French territories in the Americas. N Engl J Med. 2018;378(11):985-994.