The Zika virus has caused at least two pregnant women in the United States to opt for abortions after being diagnosed, U.S. health officials reported on Friday.

In a case study published on Friday, the Centers for Disease Control announced that it has been tracking the cases of nine pregnant women in the U.S. with confirmed Zika infections, two of whom experienced miscarriages, and two who chose to terminate their pregnancies. In one of the abortion cases, the fetus was shown to have "brain abnormalities," the CDC said.

CDC - cdc.gov

The mosquito-borne, sexually transmissible Zika virus has been linked to severe birth defects in newborns, and its spread in recent months has drummed up concern among some pregnant women who fear they may have been exposed to the virus by traveling to affected areas. All of the women being monitored by the CDC — including another 10 who are suspected of having the disease — likely contracted the virus while traveling abroad in Central and South America.

The CDC recommends that pregnant women avoid traveling to affected areas and to be cognizant about sexual activity that could lead to infection.

"For the American public, the bottom line hasn't changed," CDC Director Dr. Tom Frieden told reporters in a conference call on Friday. "If you are pregnant, avoid travel to a place where Zika is spreading."

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Zika cases are not guaranteed to cause birth defects; out of three infected women who gave birth, only one delivered an infant with severe defects. Still, the virus has caused a spike in concern among pregnant women, with some 257 people asking to be tested for the disease between August, 2015 and February 10, the CDC said. But only three percent of that number actually tested positive for the virus.

The report highlights what has become a controversial recourse for infected pregnant women — especially in countries where the virus is the prevalent. Last week, ATTN: highlighted a Washington Post story detailing how pregnant women in Latin America are desperately seeking out abortions, but running into legal barriers. One Colombian woman wrote to the Post in an email:

"I dare to write you because I’m a resident in Colombia and here the Zika virus is a major problem, although the health authorities haven’t recognized it. I want to ask for help because I’m overcome by fear that my baby will be born sick. I already have two girls and work long and hard as a single mother to provide for them. Life in Bogotá is difficult enough without being in charge of a sick child, especially with the health system so precarious in Colombia."

According to the CDC, there have been 107 reported travel-related cases of the virus across the U.S. 14 other unconfirmed cases of sexually transmitted Zika virus are being investigated by federal and state health officials.