A month after confirming Zika causes birth defects, CDC researchers say there is a "substantial" risk that a pregnant woman will have a baby with a birth defect if infected with Zika during her first trimester. More specifically, the risk for microencaphaly is 1% to 14% depending on the scenario, reports the AP. The range is wide given that research into the disease is relatively new. For the study, scientists analyzed data from 400 babies diagnosed with microcephaly—in which babies are born with abnormally small heads—in the Brazilian state of Bahia between July and February. Because the study focused exclusively on microcephaly in a single Brazilian state, "these numbers are probably only the tip of the iceberg," says a UCLA professor.
One notable quirk: the bigger the outbreak, the better the odds are of having a healthy baby—because more women would be exposed before becoming pregnant and perhaps develop immunity. When the outbreak is small, the risk rises to the 14% level. An earlier study out of Brazil put the risk of Zika-related birth defects and fetal death at almost 30%, though one based on a Zika outbreak in French Polynesia put the risk of microcephaly at 1%. But even a 1% risk could be devastating in developing countries, where there are limited care options for disabled children, a health expert tells USA Today. A separate study published Wednesday notes three Brazilian infants with microcephaly showed eye problems not linked to Zika before, including retinal lesions, hemorrhaging, and abnormal blood vessel development, per a release. (The number of pregnant women with Zika in the US has nearly tripled.)