A small case study released today by the Centers for Disease Control and Prevention (CDC) supports the agency's suspicion that when pregnant women contract the Zika virus there is higher risk for adverse outcomes for the fetus, including microcephaly.
That risk appears especially associated with a Zika infection in the first trimester of pregnancy.
The discouraging news came on the same day that the CDC issued a new travel alert recommending that pregnant women not go to the Summer Olympics in Brazil, which is experiencing surges in both Zika infections and infants with microcephaly. The agency also announced that it is establishing a special registry for pregnant women in the United States who contract the virus to better understand this public health threat.
In the latest edition of the agency's Morbidity and Mortality Weekly Report (MMWR), CDC investigators outline the cases of nine pregnant women who became infected with the Zika virus after traveling to an area of active transmission. None of them died or were hospitalized. One woman who experienced Zika symptoms in her third trimester delivered a healthy infant, as did a woman whose symptoms appeared in the second trimester. The pregnancy of another woman with second-trimester symptoms is continuing.
For six women who reported Zika symptoms in their first trimester, the outcomes were mostly grim. Two of them miscarried, two aborted their pregnancies, and another delivered an infant with microcephaly. The sixth woman has yet to deliver her child.
One woman chose to end her pregnancy after an ultrasound suggested the absence of the corpus callosum, ventriculomegaly, and brain atrophy at the 20-week mark. A follow-up fetal MRI revealed severe brain atrophy. Reverse transcription polymerase chain reaction testing detected the RNA of Zika virus in the woman's amniotic fluid.
The MMWR article did not provide details about the other woman who had an abortion, or the health status of her fetus. Denise Jamieson, MD, MPH, a member of the agency's Zika response team, said at a news conference today that there was no additional information on the second terminated pregnancy. Dr Jamieson coleads a section of the team focused on pregnancy and birth defects.
The results of the case study, small as it was, were surprising, she said.
"We did not expect to see these brain abnormalities in this small case series of US pregnant travellers," Dr Jamieson said. "It is…greater than what we would have expected."