How Dangerous Is Zika for Babies? Scientists Try to Figure Out the Answer
Nielsen and her colleagues recently followed 117 women in Rio de Janeiro with confirmed Zika infections during their pregnancies. All these women gave birth to live babies. Four percent of the babies had microcephaly. But nearly 38 percent of them had problems other than microcephaly, either at birth or three months later.
“We had babies that had abnormal MRI exams of their brains, babies with eye abnormalities, babies who failed hearing tests and appeared to have significant hearing loss,” Nielsen says. “And we had babies with fetal growth restriction” — a condition in which the fetus doesn’t grow as it should in the uterus. In some cases, the mom was infected late in pregnancy, during the third trimester, and her baby still had problems. In contrast, with microcephaly, there appears to be little risk when the Zika infection occurs late in pregnancy.
When Nielsen and her team saw how many babies had problems — more than 40 percent — they didn’t believe the data at first. “We said, ‘Wow that’s really high. That’s absurd,’ ” she says. “But then we looked at the data over and over again and we said, ‘No it’s correct.’ “