Understanding the magnitude of risk associated with Zika virus infection in pregnancy.

In any pandemic, accurate data regarding adverse perinatal outcomes are critical to clinical management, a current reality with COVID-19. During the Zika virus epidemic, initial data regarding perinatal infection risks were concerning, with adverse pregnancy outcomes reported among 46.7% of affected pregnancies (Brasil et al NEJM 2016; 375: 2321). However, subsequent data demonstrated that the incidence of birth defects attributable to Zika virus was approximately 6%, with most of the risk occurring from first trimester infection (Honein et al JAMA 2017;317: 59). These studies demonstrated that risk estimates are subject to how cohorts are established and how risk is defined.