Zika Virus–Associated Birth Defects: What Are the Risks?

March 14, 2017

Zika Virus–Associated Birth Defects: What Are the Risks?

  1. Deborah Lehman, MD

The prevalence of Zika-associated birth defects has increased 20-fold since the virus's introduction in the U.S.

  1. Deborah Lehman, MD

Infants born to women infected with Zika virus during pregnancy are at elevated risk for birth defects involving the brain and eye. Although those defects are increasingly better defined and include microcephaly, neural tube defects and eye abnormalities, the exact risks for birth defects from Zika remains uncertain because baseline risks for those defects are not defined.

CDC researchers estimated prevalence rates of specific birth defects associated with Zika virus infection before and after its introduction in the Americas. Using surveillance data from Massachusetts (2013), North Carolina (2013), and Atlanta, Georgia (2013–2014), they identified 747 infants and fetuses meeting the congenital Zika case definition (microcephaly and other brain abnormalities, neural tube defects, and eye abnormalities), for a prevalence of 2.9 per 1000 live births. Using data from the first 9 months of 2016 from the U.S. Zika Pregnancy Registry, they identified 26 affected infants out of 442 completed pregnancies with laboratory evidence of Zika virus, for a prevalence of 59 per 1000. This represents a 20-fold increase in the prevalence of Zika-associated birth defects between these two time periods.


Although we still have much to learn about this new congenital viral infection, it is clear that the risk to the fetus is significant. This study provides estimated baseline risks for specific Zika-associated birth defects in the pre-Zika era, allowing for a better assessment of the risks of a Zika-affected pregnancy now, which is critical for those counseling pregnant women.

Editor Disclosures at Time of Publication

  • Disclosures for Deborah Lehman, MD at time of publication Leadership positions in professional societies AAP PREP The Course (Member, Planning Committee)


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