About one in 10 pregnancies in the United States among women with laboratory-confirmed Zika virus infection resulted in a fetus or infant with birth defects associated with the virus in 2016, according to CDC report released Tuesday.
According to the New York Times, the report is the most comprehensive to date on the effect the Zika virus had on U.S. pregnancies.
For the report, researchers looked at pregnancies reported to the U.S. Zika Pregnancy Registry (USZPR) between Jan. 15, 2016, and Dec. 27, 2016. CDC created the registry in early 2016 to track the pregnancies of women with lab evidence of possible recent Zika infection.
According to CDC, a total of 1,297 pregnancies with lab evidence of Zika infection were reported to USZPR last year. The reports included pregnant women living in a total of 44 states. The researchers said 972 of the pregnancies were considered completed. Those pregnancies included 895 livebirths and 77 pregnancy losses, which the researchers said include abortions, miscarriages, and stillbirths.
The researchers said Zika-related birth defects were reported in 51 of the 972 completed pregnancies. In all 51 of those cases, the Zika infections were acquired outside of the continental United States, the Times reports.
According to the researchers, 250 of the 972 completed pregnancies involved women with lab-confirmed Zika infection. Of those 250 pregnancies, 24, or about 10 percent, resulted in birth defects. Further, the researchers found that the risk of birth defects was higher—by about 15 percent—in cases in which women with lab-confirmed Zika infection were infected with the virus during their pregnancies' first trimesters.
According to the researchers, the proportion of pregnancies that resulted in birth defects among women who reported symptoms of Zika infection was similar to the proportion among women who did not report symptoms of the infection. However, the researchers noted that they might not be aware of all asymptomatic cases of Zika infection because some women who were infected but did not experience symptoms might not have been tested for the virus. About 80 percent of Zika cases are asymptomatic, according to the Times.
Further, the researchers said although CDC recommends all infants born to women who might have been infected with Zika receive brain scans, they found that just 221 of the 895 live-born infants received neuroimaging. In addition, about one-third of such infants did not receive Zika testing at birth, the researchers found.
Report co-author Margaret Honein, chief of CDC's division on birth defects, said the report might "understimat[e] the complete number of infants with birth defects" resulting from Zika-infected pregnancies because "not all these babies are receiving brain imaging." She added, "It's really key for these babies to have a head ultrasound or CT scan to look for abnormalities that may not be apparent at birth."
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Acting CDC Director Anne Schuchat voiced similar concerns, saying, "I think it is very likely that we are underestimating the birth defects that follow Zika in pregnancy," adding, "Some babies that are born looking pretty much OK are eventually diagnosed with some effects of congenital Zika syndrome."
Schuchat also stressed that Zika "is not going away" and is not "something that only the [doctors] in Florida need to worry about." Noting that Zika-infected pregnancies were reported in 44 states, Schuchat added, "Clinicians in every state need to know" (Sun, "To Your Health," Washington Post, 4/4; Reynolds et al., Morbidity and Mortality Weekly Report, 4/4; Belluck, New York Times, 4/4; Walker, MedPage Today, 4/4; Doucleff, "Shots," NPR, 4/4).
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