This is the first research to quantify the risk for a pregnant woman with Zika having a baby who develops microcephaly.
pregnant woman at ultrasound
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Much has been made recently of a possible link between the Zika virus and babies born with microcephaly, a birth defect that typically includes a smaller-than-average head and brain damage. Now, a new study published today in The Lancet provides more evidence the mosquito-borne illness is causing the startling rise in this particular birth defect.

Researchers looked at data from a 2013-2014 Zika outbreak in French Polynesia and estimated the risk of microcephaly is about one for every 100 women infected during the first trimester of pregnancy.

"Data from French Polynesia are particularly important since the outbreak is already over. This provides us with a small, yet much more complete dataset than data gathered from an ongoing outbreak," explains professor Arnaud Fontanet, co-author of the study, adding, "Much more research is needed to understand how Zika might cause microcephaly."

Another recent study found adverse health effects are associated with contracting the virus at any stage of pregnancy. But according to this new study, a fetus developing microcephaly may be the most common defect of a first trimester infection given the timing of brain development.

Researchers don't know if the microcephaly rate they noted in French Polynesia will hold true for other countries experiencing outbreaks of the virus. There are other causes of microcephaly, such as other viruses like rubella, and infections like toxoplasmosis. All told, about two per 10,000 babies are born with microcephaly in Europe and Brazil, according to a press release.

This newest analysis is aimed at arming the public with better information about how Zika may impact a fetus. The hope is that by quantifying the risk, the response will also improv —something every woman of childbearing age is sincerely hoping for.

Melissa Willets is a writer/blogger and a mom. Follow her on Twitter (@Spitupnsuburbs), where she chronicles her love of exercising and drinking coffee, but never simultaneously.