Zika and the risk of microcephaly

Zika virus (ZIKV) infection during pregnancy has been linked to birth defects, yet the magnitude of risk remains uncertain. Investigators studying the 2013–2014 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 to 1.91), on the basis of eight microcephaly cases identified retrospectively in a population of approximately 270,000 people with an estimated rate of ZIKV infection of 66%.