Dr. Margaret Honein, chief of the CDC's birth defects branch, said the agency is aware of "less than a dozen" babies or fetuses who have suffered the consequences of Zika infection, which can include devastating neurological birth defects. However, she emphasized that most of the 157 pregnancies are ongoing, so it's not known how many babies will suffer.
"The CDC's top priority in the Zika response is protecting pregnant women and their fetuses," Honein said.
Not a single person is known to have contracted Zika from a mosquito bite in the U.S. They've gotten it while traveling to a country where Zika is endemic, or they've contracted it sexually from a male partner who's traveled to one of those areas.
Just this week, the CDC's website reported that there 48 pregnant women with Zika in the U.S.
The jump to 157 happened for two reasons. First, more women have become infected over time. Second, the CDC changed its system for reporting cases and now includes women who were infected but didn't have symptoms.
That's because even when a woman doesn't have symptoms of Zika, the fetus can still suffer devastating consequences from the virus.
The agency reported an additional 122 pregnant women with Zika in the U.S. territories, including Puerto Rico.
The CDC doctors said there's not enough data to predict the chances that a pregnant woman would give birth to a baby with microcephaly or any of the other devastating defects associated with the virus.
They also said they didn't know whether any of the pregnant women in their report contracted the disease sexually from a male partner or whether all of the women caught it from a mosquito bite while traveling outside the U.S.
Earlier Friday, the World Health Organization said
the same strain of the virus -- which is spreading throughout the Americas and is linked to microcephaly and other neurological disorders -- has spread to the African nation of Cabo Verde, also called Cape Verde.
"The findings are of concern because it is further proof that the outbreak is spreading beyond South America and is on the doorstep of Africa," said Dr. Matshidiso Moeti, WHO's regional director for Africa. The strain, called the Asian type, was most likely imported from Brazil, according to the WHO.
There are more than 7,500 suspected cases of Zika virus in Cape Verde and at least three cases of microcephaly. One of those is a baby born in Boston.
President Obama was briefed by top health officials from the CDC, the National Institutes of Health and the Department of Health and Human Services on Friday, after which he said, "This is something that is solvable. It is not something that we have to panic about, but it is something that we need to take seriously."
He used the opportunity to restate the need for lawmakers to approve his requested funding bill