The epidemic transmission of Zika virus (ZIKV) in Brazil has been identified as a cause of microcephaly and other neurological malformations in babies of ZIKV-infected women. This study provides a descriptive analysis, since the onset of symptoms to the delivery, of a cohort who were registered as having ZIKV infection in pregnancy, from November 2015 to December 2016. Suspected cases were registered at a referral center for infectious and tropical diseases in Manaus, in the Brazilian Amazonian region. A total of 834 women with suspected ZIKV in pregnancy were included, of whom 91.4% had confirmed pregnancy. Reverse-transcriptase polymerase chain reaction (RT-PCR) confirmed ZIKV infection in 42.2% of the cohort. In 35.2% of the cohort, ZIKV was the sole infection identified. Severe adverse pregnancy outcomes (abortion, stillbirth, or microcephaly) were observed in both RT-PCR ZIKV-positive (4.96%) and ZIKV-negative (2.15%) cases. Women with suspected ZIKV infection were much more likely to have adverse pregnancy outcomes if they were symptomatic during the first trimester of pregnancy (odds ratio 10.5; 95% confidence interval 4.0–27.0; p<0.001). Among pregnant women with suspected ZIKV infection, the occurrence of symptoms in the first trimester is associated with an especially high risk of severe adverse pregnancy outcomes.