Five per cent of women in the US territories who were infected with the Zika virus while pregnant had fetus or babies with defects, including microcephaly, government health data said on Friday.
The report by the US Centers for Disease Control and Prevention covered the US territories of Guam, American Samoa, the US Virgin Islands, Micronesia, the Republic of Marshall Islands and Puerto Rico.
The report is the first based on data from the US territories and the largest study of its kind to date.
CDC experts said the findings are consistent with previous findings about Zika cases in the mainland United States.
“Women in the US territories and elsewhere who have continued exposure to mosquitoes carrying Zika are at risk of infection,” said CDC acting director Anne Schuchat.
“We must remain vigilant and committed to preventing new Zika infections.”
The rate of birth defects was slightly higher — eight percent, or one in 12 — in women whose infections were confirmed early in the pregnancy, during the first trimester, said the report.
The findings were based on the cases of 2,549 women with possible Zika virus infection who completed their pregnancies.
Among these women, 1,508 had confirmed Zika virus infection from January 1, 2016 to April 25, 2017.
Over 120 pregnancies resulted in Zika-associated birth defects, including infants born with unusually small heads, an irreversible condition known as microcephaly.
Other complications in babies included seizures and problems with movement, coordination, eating and near constant crying.
Zika can be spread by the bite of infected mosquito or via sexual contact.
Pregnant women are urged to avoid areas where Zika is spreading.
Since Zika erupted on a large scale in mid-2015, more than 1.5 million people have been infected, mostly in Brazil and other countries in South America.
Some 70 countries have been impacted. Zika may lead to an itchy rash and although it is dangerous for pregnant women and their fetuses, it often causes no symptoms in adults.
In November 2016, the World Health Organization announced that the Zika virus outbreak no longer poses a world public health emergency, though it warned the epidemic remains a challenge.