INTRODUCTION
Zika virus (ZIKV) infection is particularly important when acquired during pregnancy. Perinatal adverse outcomes have been linked to pregnancy losses or fetal neurological damage1,2. Adverse effects following maternal ZIKV infection have been previously reported, but there is limited data available from large cohorts of ZIKV-infected mother-infant pairs. A wide variety of inclusion criteria and definitions of adverse outcomes have been used for prevalence estimates of abnormalities ranging widely from 5-46%3-13. Further, the impact of the gestational age of maternal infection on the risk of fetal abnormalities has not yet been fully defined.
Although the epidemic phase of ZIKV infection is over, there is still interest on enhancing knowledge about mother-to-child transmission and its consequences to the infant, since the endemic spread is continuing globally14 and could reemerge as a public health problem due to socioeconomic or climatic changes15.
In 2016, a large cohort of ZIKV-infected symptomatic pregnant women and their infants was composed in Ribeirão Preto metropolitan region, Brazil. Our primary objective was to investigate the prevalence of adverse pregnancy and early neonatal outcomes with an emphasis on pregnancy losses, microcephaly, and Congenital Zika Syndrome (CZS) as functions of the gestational age of maternal infection. A subset of infants had received an additional specialized evaluation within three months of life, allowing us to estimate the probability of occurrence of early-presenting occult/mild end-organ disease among infants who had not been identified affected at birth.