One in 12 infant or fetus born to mothers from the U.S. territories with laboratory-confirmed Zika infection during the first trimester had a birth defect possibly-associated with the infection, officials from the Centers for Disease Control and Prevention reported.
Overall, there were 3,930 pregnant women with laboratory evidence of possible Zika infection reported in the U.S. territories during Jan. 1, 2016-May 24, 2017. Of the 2,549 completed pregnancies, 122 resulted in a fetus or infant with possible Zika-related birth defects. The greatest number of birth defects was for maternal infections in the first trimester at 8%, followed by 5% in the second trimester, and 4% in the third trimester (MMWR. 2017, June 8.).
“These data indicate that Zika virus is associated with risks to pregnant women and their babies, even when the infection is identified later during pregnancy,” Dr. Schuchat said. “Although we are still learning about the full range of birth defects that can occur within a woman infected with Zika during pregnancy, we know that it causes brain abnormalities, vision problems, and other consequences of brain damage that might require long-term specialized care.”
In depth analysis of Zika side effects among the studied population found that 108 (89%) of the 122 fetuses or infants with infection confirmed by nucleic acid testing were diagnosed with brain abnormalities and/or microcephaly.
Researchers also found potential gaps in the evaluation of infants at birth with possible congenital Zika virus infections in the U.S. territories, according to, a coleader of the CDC Pregnancy and Birth Defects Task Force.
“There are still opportunities to ensure every health care provider is aware of how to screen for exposure to Zika, the need for comprehensive evaluation of infants, and how to monitor and provide follow-up care,” Dr. Honein said. “Identification and follow-ups with laboratory evidence of Zika infection during pregnancy can facilitate timely and appropriate clinical intervention services and help assess their future needs.”
This research was limited by the size of the population analyzed, which was small and, therefore, may not be the full scope of the Zika population. The clinical guidance for infants was also changed in August of 2016, which may have affected reporting, officials said.
To help collect more accurate data, U.S. territories will begin using the same standard case definition as used by the U.S. states and Washington, DC starting June 22, 2017.
One of the investigators reported personal fees from Population Services International, Dexis Consulting Group, and Public Health Institute outside the submitted work. The other investigators reported no relevant financial disclosures.