A report from the U.S. Zika Pregnancy and Infant Registry looked at pregnancies where there was laboratory evidence of a confirmed or possible Zika virus infection. The goal was to understand the frequency of specific birth defects known to be associated with Zika, such as microcephaly (an abnormally small head) and other brain abnormalities.
The report confirmed that these Zika-associated birth defects occurred in this group. However, the registry report did not provide specific numbers, percentages, or a comparison to pregnancies without Zika infection. This means we know the defects happened, but we don't know from this data exactly how common they were.
It is important to be careful with this information. Because this is an observational report from a registry and not a controlled study, it cannot prove that Zika virus caused the defects or determine the exact risk. The data helps with ongoing monitoring but does not give a complete picture of the likelihood of these outcomes. Readers should see this as a confirmation that the link exists, consistent with prior knowledge, but not as new data quantifying the risk.