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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.
Honein MA et al. Birth defects among fetuses and infants of US women with evidence of possible Zika virus infection during pregnancy. JAMA 2017 Jan 3; 317:59. (http://dx.doi.org/10.1001/jama.2016.19006)
Muller WJ and Miller ES.Preliminary results from the US Zika pregnancy registry: Untangling risks for congenital anomalies. JAMA 2017 Jan 3; 317:35. (http://dx.doi.org/10.1001/jama.2016.18632)
Comment
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.