The C.D.C. analysis, led by Dr. Rasmussen, was published Wednesday in The New England Journal of Medicine, and involved weeks of research into findings that have emerged from Brazil and elsewhere, including studies of fetuses with microcephaly in pregnant women infected with Zika.

The authors said they used established frameworks for assessing whether evidence met scientific criteria proving that one factor causes another. Those criteria included the existence of cases of microcephaly that have been strongly linked to documented exposure to Zika virus. Dr. Rasmussen and her colleagues also reviewed the biologically plausible explanations for how the virus might cause damage to the brain, and the absence of other explanations that make sense.

Infectious disease experts welcomed the announcement.

“The important part is that the C.D.C. can now take action without having to spend time trying to confirm the link,” said Dr. Eric J. Rubin, an infectious disease expert at Harvard and an editor at The New England Journal of Medicine.

Michael T. Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, said the C.D.C.’s announcement was a “good call,” adding “I give them credit for making clear and unambiguous statements about the neurologic complications.”

About 700 people in the United States have been infected with the Zika virus as of last week, including 69 pregnant women, Dr. Anne Schuchat, the deputy director of the C.D.C., said on Monday at a White House briefing. About half of the cases are in Puerto Rico, where the virus is circulating locally. Most of the other American cases have occurred in people who traveled to South America.

But Dr. Schuchat said that mosquitoes that can transmit Zika are present in 30 states during the warmer months, a much larger swath of the United States than health officials initially expected.