Zika infections in the third trimester don’t appear to cause birth defects

Zika Virus

A study of Zika infections in Colombia has found no obvious birth defects when women become infected with the virus in the third trimester of pregnancy.

“It’s somewhat reassuring that it looks like third-trimester infections aren’t posing a major risk of that very serious outcome,” said Dr. Margaret Honein, chief of the birth defects branch at the U.S. Centers for Disease Control and Prevention.

Honein was one of the authors of the study published online on Wednesday in the New England Journal of Medicine. She stressed that the findings were still preliminary and “it is critically important” to continue following these babies to look for other effects from exposure to Zika.

The potential effects of Zika infection include such things as hearing loss or vision problems, or any other developmental problems.

Zika virus has been shown to attack fetal brain cells and cause microcephaly, a birth defect marked by small head size and underdeveloped brains.

The Colombian study involved data on 65,726 Zika cases reported between Aug. 9, 2015 and April 2, 2016. These included 1,850 pregnant women in which the researchers knew the trimester in which the mother became infected.

Of the 600 women infected during their third trimester, 90% have delivered their babies, and none gave birth to a child with microcephaly or other obvious birth defects.

“I think the numbers are going to come up,” said Honein, who expects increasing reports of microcephaly, brain anomalies and other birth defects among women infected with Zika earlier in their pregnancies.