The rate of certain birth defects among Zika-infected pregnant women in the U.S. was 20 times higher in 2016 compared to when the virus was first introduced into the Americas, according to a CDC report.
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Using data from the U.S. Zika Pregnancy Registry, the study examined 442 completed pregnancies between Jan. 15 and Sept. 22 of last year. Researchers then compared it to population-based birth defects data collected in Massachusetts, North Carolina and Atlanta between 2013 and 2014, before the introduction of the Zika virus.
The pre-Zika data included 747 infants and fetuses with one or more birth defect such as microcephaly or brain abnormalities, neural tube defects and other early brain malformations, eye abnormalities and other central nervous system issues. The prevalence of these birth defects in the pre-Zika era represented 2.86 per 1,000 live births in the three states studied, according to the analysis.
However, data from last year reported 26 infants and fetuses with these same defects among 442 completed pregnancies involving mothers with possible Zika infection during pregnancy, according to the CDC. This reflected a prevalence of 58.8 per 1,000 live births, more than 20 times the previous prevalence of 2.86 per 1,000 live births.
"Although the ascertainment methods differed, this finding was approximately 20 times higher than the proportion of one or more of the same birth defects among pregnancies during the pre-Zika years. These data demonstrate the importance of population-based surveillance for interpreting data about birth defects potentially related to Zika virus infection," federal health officials said.