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In US territories, birth defects in 5% of pregnancies affected by Zika
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In U.S. territories, around 5% of pregnancies in women with laboratory evidence of recent possible Zika infection have resulted in a fetus or baby with birth defects, according to data released today by the CDC.
Surveillance data from five U.S. territories, including Puerto Rico, showed that the proportion of Zika-related birth defects was slightly higher — 8% — when the mother was infected in the first trimester.
The percentages are not statistically different than those reported earlier this year for the primarily travel-related Zika cases in 50 U.S. states. The CDC reported in April that 5% of pregnancies with laboratory evidence of Zika infection in U.S. states resulted in birth defects, including 15% in women who were infected in the first trimester.
But the CDC said both sets of estimates, based on relatively small numbers of pregnancies, were “not statistically different” and represented a “snapshot in time” of an emerging health issue.
“The bottom line for women is that there is no doubt that Zika virus infection during pregnancy diagnosed during any trimester can lead to severe birth defects,” acting CDC Director Anne Schuchat, MD, said during a telebriefing.
Overall, researchers analyzed data on 2,549 possible Zika-affected pregnancies that occurred between Jan. 1, 2016, and April 25, 2017, in American Samoa, the Federated States of Micronesia, the Marshall Islands, Puerto Rico and the U.S. Virgin Islands, including 1,508 laboratory-confirmed cases. The cases included live births and pregnancy losses at any gestational stage reported to Zika pregnancy and infant registries established by the CDC.
Among them, 122 infants or fetuses met the CDC surveillance case definition as having possible Zika-associated birth defects, including 108 (89%) classified as having brain abnormalities or microcephaly, or both, the researchers said.
The proportion of possible affected pregnancies that ended in birth defects varied according to the trimester in which the mother was infected, from 8% in the first trimester to 5% in the second trimester and 4% in the third trimester.
Overall, cases occurred in 5% of symptomatic and 4% of asymptomatic women. In pregnancies in which infection was confirmed, these percentages were 5% and 7%, respectively.
Based on data from the territories, 59% of infants born to women with laboratory-confirmed Zika infection were tested for Zika at birth. Among the 2,464 live-born infants, 52% were reported to have received recommended neuroimaging — much higher than the 25% of infants reported to have received it in the U.S.
The CDC did not sort the data by territory and neither Schuchat nor Peggy Honein, PhD, MPH, who co-leads the CDC task force on Zika-related pregnancy and birth defects, would say how many cases came from Puerto Rico, one of the countries hit hardest by the Zika virus epidemic.
Last fall, the CDC stopped reporting Zika-related pregnancy outcomes from U.S. territories because some — particularly Puerto Rico, according to reports — were not using the standard CDC surveillance case definition, in effect downplaying the extent of the problem. But Honein said the agency would resume reporting such data from U.S. territories later this month after all agreed to use the CDC definition. She said territory-level health departments may still publish data that conflict with CDC reports.
Puerto Rico, which recently declared its Zika outbreak to be over, has reported 38 cases of congenital defects related to Zika infection.
“Each jurisdiction may define a different case definition for reporting on their own website,” Honein said. “However, in this report and for CDC’s regular reporting purposes, starting on June 22, all U.S. territories have expressed their agreement with using the same standard CDC surveillance case definition as the U.S. states and [Washington] D.C.”
Schuchat said the CDC was using emergency funds set aside for fiscal year 2017 to continue operating the Zika pregnancy registries and could not say how surveillance would be funded in the future as concerns grow that federal support may be withdrawn.
“We are very appreciative of those resources and that’s the focus of the work going on right now,” Schuchat said of the emergency funds. “I can’t really speculate about future funding, but those are the resources that are providing support for the registries right now.”
Zika is primarily spread through the bite of an infected Aedes aegypti mosquito but also can be sexually transmitted by both women and men. In March, the CDC updated its travel guidance to recommend that pregnant women avoid any areas where there is a risk for Zika infection. The agency also recommends that women avoid unprotected sex with a partner who has traveled to an active Zika area.
“It’s very important to try to avoid Zika exposure during pregnancy, whether that’s mosquito exposure or sexual exposure,” Schuchat said. “And it’s very important to get tested if you are exposed or living in one of those areas and to have the babies followed up carefully. This is a very dangerous virus in the context of a pregnancy.” – by Gerard Gallagher
Reference:
Shapiro-Mendoza CK, et al. MMWR Morb Mortal Wkly Rep. 2017;doi:10.15585/mmwr.mm6623e1.
Disclosure: Honein, Schuchat and the researchers report no relevant financial disclosures.