A study on pregnant women and Zika conducted by scientists in Colombia may indicate Zika infections during the third trimester of pregnancy are unlikely to cause severe birth defects such as microcephaly.
In what has been called a "preliminary report" from a larger study that looks at thousands of pregnant women, researchers have examined the pregnancies of almost 600 women who were infected with Zika during the third trimester of pregnancy, according to NPR.
According to the researchers' findings, none of the women who contracted Zika in the third trimester gave birth to a baby with microcephaly. Researchers have said that while the study has indicated that the risk of birth defects is lower if the mother contracts Zika the third trimester, there is still more work to be done.
"I think it's somewhat reassuring that there were not major birth defects identified," Dr. Margaret Honein, an epidemiologist working with the Centers for Disease Control and Prevention, told NPR. "But I want to make sure we understand there is still a lot that we need to know."
The link between third-trimester Zika infections and other complications, such as miscarriage or stillbirths, for example, remains unclear. Another study which was published in February found that Zika infections during late pregnancy may increase the risk for those complications.
The study is also following the babies born in the study for at least one year, to see if problems develop later.
"Even simply having influenza during pregnancy increases the risk of lifelong issues, such as a higher rate of schizophrenia later in life," said Dr. Catherine Spong, acting director of the National Institute of Child Health and Human Development. "We don't have the full picture for how Zika impacts pregnancy."
Health officials at the CDC have reported the number of pregnant women in the continental U.S. who have been infected with Zika has risen to 234, according to The New York Times.
The CDC also cited six cases of abnormalities in birth from U.S. pregnancies where the mother had contracted Zika. The cases included three babies born with birth defects and three who died before birth but had evidence of birth defects.
"Microcephalic babies are beginning to be born," said Dr. Denise Jamieson, a leader of the pregnancy and birth defects team at the CDC. "The disease seems to be very similar no matter where it is."