Abstract

Zika virus (ZIKV) infection during pregnancy has been linked to birth defects,1 yet the magnitude of risk remains uncertain. A study of the Zika outbreak in French Polynesia estimated that the risk of microcephaly due to ZIKV infection in the first trimester of pregnancy was 0.95% (95% confidence interval: 0.34-1.91%), based on eight microcephaly cases identified retrospectively in a population of approximately 270,000 people with an estimated 66% ZIKV infection rate.2