Roughly 6% of infants or fetuses in the U.S. developed Zika-related birth defects when their mothers had Zika virus infection during pregnancy, according to a new report.
The authors, who included experts from the Centers for Disease Control and Prevention (CDC), said the findings highlight the importance of protecting pregnant women from the infection and testing those who may have been exposed as well as their babies.
The findings were released Tuesday in the report “Birth Defects Among Fetuses and Infants of US Women With Evidence of Possible Zika Virus Infection During Pregnancy” (Honein MA, et al. JAMA. Dec. 13, 2016, http://jamanetwork.com/journals/jama/fullarticle/2593702).
Researchers used data from the U.S. Zika Pregnancy Registry to analyze pregnancy outcomes for women with possible Zika infection reported in the continental U.S. and Hawaii from Jan. 15 to Sept. 22. Among 442 completed pregnancies, 26 fetuses or infants (6%) had a Zika-related birth defect — 21 among the live births and five among the pregnancy losses.
Roughly 4% of all exposed infants and fetuses were diagnosed with microcephaly, the birth defect that sparked initial concern about the virus earlier this year. The microcephaly rate far surpassed the typical rate of 0.07% when Zika is not involved.
The rate of birth defects was the same regardless of whether the mother was symptomatic, according to the report. However, the team found exposure in early pregnancy to be especially concerning. About 11% of fetuses and infants had a birth defect when their mother was exposed exclusively in the first trimester.
All of the mothers’ Zika infections were determined to be travel-related. Among the women whose children developed birth defects, the exposure could be traced back to Barbados, Belize, Brazil, Colombia, Dominican Republic, El Salvador, Guatemala, Haiti, Honduras, Mexico, Republic of Marshall Islands and Venezuela.
“The findings in this report emphasize the need for pregnant women to avoid travel to areas with active Zika virus transmission and consistently and correctly use condoms to prevent sexual transmission throughout pregnancy if their partner has recently traveled to an area of active Zika virus transmission,” authors wrote.
They also highlighted the need to follow CDC guidance on testing fetuses and infants born to mothers who may have contracted Zika during pregnancy. Roughly 12% of the infants with birth defects and 41% of all infants born to infected mothers had not been tested.