More Than Microcephaly: Congenital Zika Syndrome

Laura A. Stokowski, RN, MS; William B. Dobyns, MD


September 21, 2016

In This Article

Timing of Zika Infection in Pregnancy

Medscape: What has been established about the timing of maternal infection and the subsequent effects on the unborn baby? The CDC says that there is no known safe time to be infected with Zika during pregnancy,[6] but the message is still out there that congenital Zika syndrome is mainly a risk when infection occurs during the first or second trimester.[7]

Dr Dobyns: One way of determining when a person is infected is to look at the onset of symptoms of a viral illness, such as a rash or fever. However, many people don't know that they have been infected with Zika virus because they aren't ill. It is estimated that 20% of people who are infected with Zika suspect that they are infected because they have symptoms. But when you look at the mothers of babies who have congenital Zika syndrome, it's a very different story.[8] The majority—64% of these mothers—had symptoms consistent with Zika virus infection. The implication is that they were sicker and, therefore, more symptomatic. If it had been the same as in the general population, we would have expected 20% of these mothers to have reported a viral syndrome with a rash. But it wasn't 20%; it was 64%. This suggests that the risk for congenital Zika syndrome in the baby is higher among pregnant woman who have a symptomatic Zika infection. Other recent studies that have demonstrated the same thing.[9]

About three-fourths of the mothers who reported an illness during pregnancy reported being ill during the first trimester; the rest reported being ill during the second trimester.[9] So, congenital Zika syndrome is predominantly related to first-trimester infection, but can follow infection in the second trimester as well.

Few mothers reported being ill during the third trimester. But it is possible that those mothers had asymptomatic Zika illnesses during the first trimester and had some other viral infection during the third trimester. We don't have data yet on third-trimester Zika infections. Only prospective studies will tell us whether infection during the third trimester can cause severe congenital Zika syndrome.

These children are profoundly handicapped, and they have already started to die in the first year of life, often within the first 6 months. Children with arthrogryposis are doing the worst, which is no surprise.

Medscape: Do we have reason to be concerned about Zika infections during the third trimester?

With the new information we have, I would be worried about the third trimester as well.

Dr Dobyns: With the new information we have, I would be worried about the third trimester as well. We have excellent documentation that first- and second-trimester Zika exposure can cause congenital Zika syndrome; there is no question about it. Although we have far less documentation about exposure in the third trimester, new reports of milder cases make me worry about the third trimester as well.

It needs to be determined what the entire set of babies from all women who had a Zika infection at any time during pregnancy—first, second, or third trimester—looks like. What proportion of them have congenital Zika syndrome and what proportion have a more subtle presentation? How old must these children be before we can test for and find subtle effects of Zika infection? We don't know, but it would be a mistake to assume that these babies have nothing.

Medscape: Should all pregnant women be tested for Zika infection?

Dr Dobyns: Doing that in Seattle would be pointless, but if I was an obstetrician in Miami, I would be checking Zika titers in my patients. I don't know what the recommendations to obstetricians will be about testing for Zika, but we already test young women of childbearing age for CMV to see whether they are immune if they work in a hospital. With Zika, the risk factor isn't working in healthcare, it's living in an area prone to mosquitoes. You can test mothers for Zika directly when they are ill or you can test for antibodies a few weeks later; you can test babies immediately after birth.


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