CDC Updates Best Estimate For The Risk Of Birth Defects After Zika Infection In Pregnant Women

In the largest study to date of completed pregnancies with lab-confirmed Zika infections, CDC reports that approximately 5% of fetuses and infants had possible Zika-associated birth defects. The data were collected from pregnancy and infant registries established by CDC in US territories over a 16 month period January 2016 thru most of April 2017. The estimate may be low since for the risk early in pregnancy since most of the infections studied had symptom onset or lab testing in the second and third trimesters.

The study involved 2,549 completed pregnancies, including both live births and pregnancy losses. Among a subset of pregnancies with more specific lab testing, the percentage of possible Zika-associated outcomes was 8% in the first, 5% in the second, and 4% in the third trimester. These included not only brain abnormalities but other neural tube defects, eye abnormalities, or CNS dysfunctions. Among completed pregnancies, most women (61%) were symptomatic, and 38% were asymptomatic.

The 2,549 completed pregnancies produced 122 possible Zika-associated birth defects, essentially as many in the asymptomatic women (4%) as in the symptomatic women (5%). Most (108) of these 122 cases of birth defects were brain abnormalities or microcephaly.

These data suggest that Zika infection anytime during pregnancy can beassociated with birth defects and monitoring is considered essential to make sure the appropriate interventions can be applied for the care of the infants.