Three infants have been born with Zika-linked birth defects in the U.S., health officials said.

The mothers of these infants were infected with Zika, and the babies were born with microcephaly, excess fluid in the brain, abnormal eye development and others, the U.S. Centers for Disease Control and Prevention (CDC) said on Thursday.

The CDC has been tracking the pregnancies of Zika-infected women since the start of the year, and so far, it had found 234 pregnant women - residents and visitors - diagnosed with Zika, Yahoo News reported.

According to the CDC, three women with Zika experienced pregnancy losses - such as abortion, miscarriages and stillbirths - involving fetuses that were said to have signs of the Zika-related defects.

While the women had Zika infections, officials said they did not know whether the birth defects were caused by the virus or other factors.

"We are trying our best to be transparent and responsive and share what we know when we know it," Dr. Denise Jamieson, chief of the Women's Health ad Fertility Branch, said in a statement published on Time.

"Because of privacy it's been challenging throughout the response to see how much we can share," Jamieson added.

The CDC said that it will begin regularly providing information about the outcomes of pregnancies for women with Zika in the U.S. based on the Zika Pregnancy Registry.

Majority of the women in the registry got the virus from traveling to affected countries, and others contracted from sexual transmission. So far, there are no cases of Zika transmitted by local mosquitoes in continental U.S.

Just recently, CDC researchers reported that about 12,000 pregnant women in the country are infected by Zika, but all women who were infected in their third trimesters gave birth to healthy babies.

This led researchers to the assumption that the risk is highest when women are infected early in the pregnancy.  

However, Jamieson said that it is still unclear whether these healthy babies will have any effects down the line.

Overall, there are 756 cases of Zika reported in the 50 states and the District of Columbia. In Puerto Rico and other territories, there are 189 pregnant women who have Zika.