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New England Journal of Medicine, 15 March 2018

Bruno Hoen, M.D., Ph.D., Bruno Schaub, M.D., Anna L. Funk, M.Sc., Vanessa Ardillon, M.D., Manon Boullard, M.Sc., André Cabié, M.D., Ph.D., Caroline Callier, M.Sc., Gabriel Carles, M.D., Sylvie Cassadou, M.D., Raymond Césaire, M.D., Ph.D., Maylis Douine, M.D., Ph.D., Cécile Herrmann-Storck, M.D., Philippe Kadhel, M.D., Ph.D., Cédric Laouénan, M.D., Ph.D., Yoann Madec, Ph.D., Alice Monthieux, M.D., Mathieu Nacher, M.D., Ph.D., Fatiha Najioullah, Ph.D., Dominique Rousset, M.D., Ph.D., Catherine Ryan, M.D., Kinda Schepers, M.D., Ph.D., Sofia Stegmann-Planchard, M.D., M.P.H., Benoît Tressières, M.Sc., Jean-Luc Voluménie, M.D., Samson Yassinguezo, M.D., Eustase Janky, M.D., Ph.D., and Arnaud Fontanet, M.D., Dr.P.H.
The risk of congenital neurologic defects related to Zika virus (ZIKV) infection has ranged from 6 to 42% in various reports. The aim of this study was to estimate this risk among pregnant women with symptomatic ZIKV infection in French territories in the Americas. From March 2016 through November 2016, we enrolled in this prospective cohort study pregnant women with symptomatic ZIKV infection that was confirmed by polymerase-chain-reaction (PCR) assay. The analysis included all data collected up to April 27, 2017, the date of the last delivery in the cohort. Among the 555 fetuses and infants in the 546 pregnancies included in the analysis, 28 (5.0%) were not carried to term or were stillborn, and 527 were born alive. Neurologic and ocular defects possibly associated with ZIKV infection were seen in 39 fetuses and infants (7.0%; 95% confidence interval, 5.0 to 9.5); of these, 10 were not carried to term because of termination of pregnancy for medical reasons, 1 was stillborn, and 28 were live-born. Microcephaly (defined as head circumference more than 2 SD below the mean for sex and gestational age) was detected in 32 fetuses and infants (5.8%), of whom 9 (1.6%) had severe microcephaly (more than 3 SD below the mean). Neurologic and ocular defects were more common when ZIKV infection occurred during the first trimester (24 of 189 fetuses and infants [12.7%]) than when it occurred during the second trimester (9 of 252 [3.6%]) or third trimester (6 of 114 [5.3%]) (P=0.001). Among pregnant women with symptomatic, PCR-confirmed ZIKV infection, birth defects possibly associated with ZIKV infection were present in 7% of fetuses and infants. Defects occurred more frequently in fetuses and infants whose mothers had been infected early in pregnancy. Longer-term follow-up of infants is required to assess any manifestations not detected at birth.