99% of Babies Born to Moms With Zika Are Normal
But rate may vary greatly by outbreak and location
By Arden Dier, Newser Staff
Posted Mar 16, 2016 7:52 AM CDT
A pregnant woman shows off her ultrasound photo in Brazil.   (AP Photo/Felipe Dana)

(Newser) – A new study on the Zika virus may or may not allay pregnant women's fears: Researchers in French Polynesia have strengthened the link between Zika and microcephaly, though they say just one in 100 pregnant women infected in the first trimester of pregnancy developed a fetus with an abnormally small brain or head. The rate—based on an outbreak from October 2013 to April 2014 during which 66% of the population was infected—"means you have a 99% chance of having a normal baby," an expert says, per the New York Times. That's remarkable considering a child born to a woman with rubella in early pregnancy has a 50% risk of birth defects, per the Guardian. However, researchers caution that the rate of microcephaly tied to Zika may vary greatly depending on the outbreak and location.

Researchers identified eight babies born with microcephaly from September 2013 to July 2015. Previously, about two cases per 10,000 newborns was the norm. Though the mothers weren't tested for Zika, seven cases were discovered around the end of the outbreak between March and July 2014 and "such temporal clustering strongly supports the proposed association" between Zika and microcephaly, researchers say. "It's still a large public health problem," a researcher notes. "Severely small heads is only 'the tip of the iceberg,' as many other birth defects are now studied as potentially correlated with Zika's infection, too, increasing the burden of disability and devastation that these babies could be facing, if they survive," a doctor adds, per Live Science. (A study on Zika-infected women in Brazil found abnormalities in 29% of fetuses.)