CHICAGO (Reuters) – A study in Brazil of 70 babies whose mothers had confirmed Zika infections found that nearly 6 percent had hearing loss, adding a new complication to the list of ills the virus can cause when women are infected during pregnancy.

The Brazilian study, published on Tuesday in the U.S. Centers for Disease Control and Prevention’s weekly report on death and disease, confirmed less rigorous reports of deafness among infants born to mothers with Zika infections.

The finding is part of an effort to fully characterize the harm caused by the Zika virus during pregnancy. The virus is best known for causing the severe birth defect microcephaly, characterized by undersized heads and underdeveloped brains. But other studies have shown that Zika can cause other brain abnormalities, vision problems and joint deformities.

In the latest study, a team led by Dr. Marli Tenório and Dr. Ernesto Marques of the Oswaldo Cruz Foundation in Pernambuco, Brazil, examined records from 70 infants with microcephaly whose mothers had laboratory-confirmed Zika infections during pregnancy.

They found that nearly 6 percent had hearing loss without any other plausible cause.

Several other viral infections during pregnancy can cause hearing loss, including rubella and cytomegalovirus, or CMV, infections. The current study adds Zika infection to that list.

Scientists say Zika should now be considered a risk factor for hearing loss, and children who were exposed during pregnancy but have normal hearing at birth should be screened regularly for delayed or progressive hearing loss.

The connection between Zika and microcephaly first came to light last fall in Brazil, which has since confirmed more than 1,800 cases of microcephaly.

(Reporting by Julie Steenhuysen; Editing by Jonathan Oatis)