Many types of viral infections, such as rubella or cytomegalovirus, can cause physical deformities and intellectual deficiencies, especially during the first three months of pregnancy, when the vital organs are being formed. Viruses can travel through the placenta and infect the foetus directly, sometimes in the brain.
Zika virus has been linked to microcephaly in infants, a condition that causes unusually small skulls and brains, and could lead to death or disability.
When a mom-to-be becomes infected with Zika virus, the virus can also infect the fetus. In Brazil, the number of cases of Zika infection and microcephalic babies spiked around the same time. Before the current outbreak, Zika infections in Brazil were extremely rare; since the outbreak, up to an estimated 1.5 million Brazilians have been infected. And between October 2015 and January 2016, more than 4,180 cases of microcephaly were reported by Brazilian health authorities; a total of only about 150 cases of microcephaly were reported annually in previous years.
That potential link is why health experts believe a Zika infection during pregnancy may lead to this rare birth defect.Microcephaly is a neurological condition where babies are born with small heads and sometimes small brains. The condition may also be associated with severe developmental issues and, in rare instances, result in death. The highest risk to the fetus is believed to be when the mother is infected during the first trimester.
It also appears that Zika infection during pregnancy may damage babies’ vision. A very small study has linked the virus to serious eye abnormalities in babies. The observed effects appear to be different from those doctors usually see in babies born with microcephaly from other causes (like rubella or toxoplasmosis). It’s not yet clear if babies born with normal-sized heads but who were still exposed to Zika may also have this eye defect, so researchers are continuing to look into this relationship.
Some research has found Zika in the brain of babies with microcephaly whose mothers contracted Zika during pregnancy. And there have been two documented U.S. cases of mothers with Zika miscarrying. That said, the CDC cautions that more research is needed to better understand the link between the Zika virus and microcephaly. The exact outcomes that might be associated with infection during pregnancy and the factors that may increase risk to a fetus are not yet fully understood.
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