The first report on the how Zika virus affected U.S. territories showed that 5% of women with confirmed infections had babies with birth defects, US health officials said on Thursday.

The report from the US Centers for Disease Control and Prevention is the first to include official numbers from the territory of Puerto Rico, which on Monday declared that its Zika epidemic had ended, based on data showing the number of new cases has fallen.

The CDC on Thursday continued to reiterate its recommendation that pregnant women not travel to Puerto Rico, noting that Zika remains a risk for pregnant women there and anywhere else the mosquito–borne virus is active.

"Zika virus poses a serious threat to pregnant women and their babies, regardless of when the infection occurs during the pregnancy,” said CDC Acting Director Dr. Anne Schuchat.

"Women in the U.S. territories and elsewhere who have continued exposure to mosquitoes carrying Zika are at risk of infection. We must remain vigilant and committed to preventing new Zika infections."

Besides Puerto Rico, the report included data on 1,508 Zika–confirmed pregnancies in women from American Samoa, the Federated States of Micronesia, the Republic of Marshall Islands, and the U.S. Virgin Islands from Jan. 1, 2016 through April 25, 2017.

Of these, more than 120 pregnancies, or about 5 percent, resulted in Zika–associated birth defects, the CDC said in its Morbidity and Mortality Weekly Report, June 8.

Among the women who were infected during their first trimester of pregnancy, 8 percent had babies with Zika–associated birth defects. That compared with 15 percent in a prior study of birth defects among women from U.S. states and the District of Colombia, most of whom became infected during travel to Zika–affected countries.

The CDC said because the newer report is much larger, the findings are not statistically different.

About 5% of women infected during their second trimester and about 4% infected in their third trimester had babies with Zika–related birth defects, showing that the virus remains dangerous throughout a woman's pregnancy.

The report represents the largest number of completed pregnancies with lab–confirmed Zika virus infections to date, the CDC said.

—Julie Steenhuysen