Locally transmitted Zika infections are on the rise in the U.S., almost entirely in Florida so far. Another potential outbreak in St. Petersburg was reported Aug. 23.

Still, physicians and other researchers are only just beginning to understand the potentially harmful effects of the virus on humans, which could be especially damaging to developing brains in fetuses.

A new presentation of research in the journal Radiology shows CT and MRI brain scans documenting the possible effects of prenatal Zika infections on babies before and after birth. The scans were taken from the children of 438 pregnant women in northeastern Brazil (“where the congenital infection has been particularly severe”) with suspected Zika infections who came to the Instituto de Pesquisa in Campina Grande State Paraiba between June 2015 and May 2016.

The researchers found brain-related birth defects to be more than just the widely cited incidence of microcephaly. Within 17 confirmed and 28 suspected congenital infections, a vast majority of the cases showed ventriculomegaly (94 percent of confirmed cases and 96 percent of suspected cases), abnormalities of the corpus callosum (94 percent of confirmed cases and 78 percent of suspected cases) and cortical migrational abnormalities (94 percent of confirmed cases and 100 percent of suspected cases). A high percentage of both groups also showed basal ganglia and/or thalamus calcification and gray matter-white matter junction calcification.

During imaging, many of the fetuses were found to have cranial circumferences below the 5^th percentile (except in three cases of ventriculomegaly, where it appeared to be normal). The researchers also described the normally visible parts of the fetuses’ heads to also appear abnormal.

“The skull frequently had a collapsed appearance with overlapping sutures and redundant skin folds and, occasionally, intracranial herniation of orbital fat and clot in the confluence of sinuses,” they wrote.

The researchers wrote that nearly all of the women included in their study suffered from a Zika-characteristic rash late in the first trimester of pregnancy, “a time of rapid brain development.” It possibly that less severe infections or infection during a different stage of pregnancy could influence these outcomes to be more or less severe in a different cohort of women.

Check out the study’s results and fetal and neonatal brain images at Radiology.