If a Pregnant Woman Gets Zika, What"s the Risk of Microcephaly for the Baby?

First Baby With Zika-Related Microcephaly Born in Continental U.S.

Zika is beyond a doubt scariest for pregnant women, or for women trying to get pregnant. For women living in areas where the mosquito-borne virus is spreading, who are trying to make the huge decision of whether, and when, to have a child, theres not a lot to go on. The Centers for Disease Control and Prevention recommends that women whove gotten Zika should wait at least eight weeks to conceive, and that men whove gotten it should wait at least six months.

But the vast majority of people who are infected with Zika dont show any symptoms, and children can still be born with birth defects and mothers can still miscarry, even if they never had symptoms. So its possible that microcephalya birth defect caused by Zika that leads to smaller-than-average head size and other developmental problemscould sneak up on parents who never knew one of them had Zika in the first place.

Margaret Chan, the director of the World Health Organization, summed up the harsh reality of the situation in her recent address to the 69th World Health Assembly: To protect women of childbearing age, all we can offer is advice. Avoid mosquito bites. Delay pregnancy. Do not travel to areas with ongoing transmission.

If a woman is infected in her first trimester, there is between a 1 and 13 percent chance of her fetus developing microcephaly.

This is not the most reassuring advice. But a new paper published in the New England Journal of Medicine estimates how likely it is that the fetus of a woman infected with Zika would develop microcephaly, offering would-be parents at least some idea of the risk theyd be taking on.

Analyzing current outbreak data from the Brazilian state of Bahia, researchers from the CDC calculated that if a woman is infected in her first trimester, there is between a 1 and 13 percent chance of her fetus developing microcephaly.

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Thats a big range! We have Zikas stealthy nature to thank for that. The first number is based on the assumption that the Zika infection rate in Bahias population is 80 percent and that half the cases of microcephaly reported are false. The second presumes a 10 percent infection rate and that every case reported is true. Theres probably been at least some overreporting of microcephaly in Brazil, and since many people dont show symptoms and dont get tested, the actual infection rate is hard to pin down. So we dont know where in that range the truth lies.

A previous analysis of the 2013-2014 Zika outbreak in French Polynesia found about a 1 percent riskbut the microcephaly cases there were found retrospectively, so that might be on the low side.

Some important caveatsthis study only looked at first-trimester infection, and infection at all stages of pregnancy has been associated with fetal abnormalities and other pregnancy problems. And it also only looked at microcephaly specifically. Microcephaly is only one possible adverse outcome among a spectrum of conditions that may be part of congenital Zika syndrome, the researchers write.

Still, at least we now have a risk estimate to offer women, along with advice.

Source: http://www.theatlantic.com/health/archive/2016/05/if-a-pregnant-woman-gets-zika-whats-the-risk-of-microcephaly-for-the-baby/484481/