December 16, 2016

Zika-Linked Birth Defects More Extensive Than Previously Thought

LOS ANGELES -- December 16, 2016 -- Zika-linked abnormalities that occur in human fetuses are more extensive and severe than previously thought, with 46% of 125 pregnancies among Zika-infected women resulting in birth defects in newborns or ending in fetal death.

The study, published in the New England Journal of Medicine, suggests that damage during fetal development from the mosquito-borne virus can occur throughout pregnancy and that other birth defects are more common than microcephaly.

In addition, these defects may only be detected weeks or months after the baby is born, according to Karin Nielsen, MD, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California.

“This means that microcephaly is not the most common congenital defect from the Zika virus,” she said.

The absence of that condition does not mean the baby will be free of birth defects, she added, because there are problems that are not apparent at birth and such difficulties may not be evident until the baby is aged 6 months.

The results are a follow-up to a smaller Brazilian study published in March that used molecular testing to find an association between Zika infection in pregnant women and a series of serious outcomes that included fetal deaths (miscarriages and stillbirths), abnormal fetal growth and damage to the central nervous system. Women were followed from the time they were infected to the end of their pregnancies. All the women were enrolled before any abnormalities in their pregnancies had been identified.

The current study was based on a larger sample size of 345 women from Rio de Janeiro, Brazil, who were enrolled from September 2015 through May 2016. Of those women, 182 (53%) tested positive for Zika in the blood, urine or both. In addition, 42% of the women who did not have Zika were found to be infected with chikungunya; 3% of Zika-positive women also had chikungunya.

From there, the researchers evaluated 125 women infected with Zika and 61 who were not infected with the virus who had given birth by July 2016. The previous study was based mainly on prenatal ultrasound findings. By contrast, the current research evaluated infants from Zika-affected pregnancies through physical examination and brain imaging.

There were 9 fetal deaths among women with Zika infection during pregnancy -- 5 of those in the first trimester. Fetal deaths or abnormalities in the infants were present in 46% of Zika-positive women, compared with 11.5% of Zika-negative women.

Of the infants born to the Zika-infected mothers, 42% were found to have microcephaly, brain lesions or brain calcifications seen in imaging studies, lesions in the retina, deafness, feeding difficulties, and other complications.

The risks occurred at all stages of pregnancy: 55% of pregnancies were affected in the first trimester, 51% in the second trimester, and 29% in the third trimester.

The researchers noted that they examined the babies during their early infancy, when more subtle neurologic manifestations of disease are not identified. Follow-up examinations could turn up evidence of more neurologic diseases that couldn’t be detected earlier in the babies’ lives.

“Our data show that the risk of severe adverse pregnancy and infant outcomes after maternal Zika infection was substantial,” the authors wrote.

SOURCE: University of California, Los Angeles (UCLA), Health Sciences

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