Objective To define the prevalence of adverse outcomes of maternal infection in a large cohort of ZIKV-infected Brazilian women and their infants. Design Prospective population-based cohort study. Setting Ribeirão Preto's region's private and public health facilities. Population Symptomatic ZIKV-infected mothers and their infants. Methods Prenatal/early neonatal data were obtained for all mother-child pairs. A subgroup of infants had cranial ultrasonography, eye fundoscopy, hearing and neurological examinations and Bayley III screening tests within 3 months of age. Conclusions This prospective population-based study represents the largest Brazilian cohort study of ZIKV in pregnancy. Congenital anomalies potentially associated with CZS are less frequent than previously thought. There is a strong association between the gestational age of infection (≤11 weeks) and a poorer early infant prognosis. A notable proportion of apparently asymptomatic newborns can present with subclinical findings within 3 months of age.