Birth defects among fetuses and infants of US women with evidence of possible Zika virus infection during pregnancy
In completed pregnancies with evidence of risk of Zika infection 6% had Zika-related birth defects, compared with women with first-trimester evidence of Zika-infection where 11% had Zika-associated birth defects – evidence for early screening for virus exposure.
Establishing the magnitude of the risk of Zika virus infection in pregnant women is important since current estimates place it between 1-13%. Previous studies have concentrated on symptomatic Zika infection, so the risk to asymptomatic women is unclear.
The study aims to establish the proportion of fetuses or infants with birth defects after maternal exposure to Zika by trimester of potential infection compared with presence of maternal symptoms.
Data was gathered from US Zika Pregnancy Register from Dec 2015 – Sept 2016. 442 completed pregnancies were identified (median age of pregnant women, 28 years; range, 15-50 years) with laboratory evidence of possible recent Zika virus infection. Birth defects potentially related to Zika virus were identified in 26 (6%; 95%CI, 4%-8%) fetuses or infants. The authors recognised that there could be selection bias and the exact timing of infection might not be accurate.