Pinning Down Risk for Zika-Linked Birth Defects

January 13, 2017

Pinning Down Risk for Zika-Linked Birth Defects

  1. Anna Wald, MD, MPH

Among 85 U.S. women with first-trimester Zika infection, 11% had offspring with birth defects; incidence of such birth defects was similar with or without maternal symptoms.

  1. Anna Wald, MD, MPH

Despite the documented link between Zika infection during pregnancy and fetal microcephaly, risk for birth defects remains incompletely characterized. Investigators analyzed data from the U.S. Zika Pregnancy Registry to evaluate pregnancy outcomes in 442 women with laboratory evidence of Zika infection during pregnancy (acquired abroad or sexually from a traveler).

Among 395 live births, 21 infants with birth defects were identified; 5 additional fetuses with birth defects were identified in 47 pregnancy losses for an overall rate of 6% (primarily brain abnormalities with or without microcephaly, and eye defects). Among pregnancies with confirmed Zika infection during the first trimester, 9 of 85 infants (11%) had such defects. In contrast, infants born following maternal Zika infection during the second or third trimester did not have birth defects. Risk for birth defects was similar for symptomatic and asymptomatic infections.


This report confirms the association between maternal Zika infection during pregnancy and abnormal fetal brain development and suggests that risk is particularly high when infection occurs during the first trimester (when organogenesis occurs); however, the potential for neurologic damage even with later infection has been reported elsewhere. Because even asymptomatic Zika infection can lead to poor pregnancy outcomes, CDC's recommendation (MMWR Morb Mortal Wkly Rep 2016; 65:739) to assess all pregnant women in the U.S. at each prenatal visit for possible Zika exposure is warranted.

Editor Disclosures at Time of Publication

  • Disclosures for Anna Wald, MD, MPH at time of publication Consultant / Advisory board AiCuris; Merck (DSMB) Royalties UpToDate Grant / Research support NIH/National Cancer Institute; NIH/National Institute of Allergy and Infectious Diseases; Genocea Biosciences; Vical Editorial boards Sexually Transmitted Diseases; Sexually Transmitted Infections Leadership positions in professional societies International Society for Sexually Transmitted Diseases Research (Board Member)


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