During the Zika virus (ZIKV) epidemic in Rio de Janeiro from September 2015 through June 2016, a prospective cohort study involving symptomatic pregnant women who had ZIKV infection confirmed by reverse-transcriptase– polymerase-chain-reaction assay was established.1 The study was approved by the institutional review boards at Fundação Oswaldo Cruz in Rio de Janeiro and the University of California, Los Angeles, and all the women provided written informed consent for themselves and their children.