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Zika virus

Serious birth defects afflict one in 10 Zika pregnancies, shocking new study reveals

PUBLISHED : Wednesday, 05 April, 2017, 2:28am
UPDATED : Wednesday, 05 April, 2017, 9:54pm

About 1 in 10 pregnant women infected with Zika in the United States last year had a baby or foetus with serious birth defects, according to the startling results of study released Tuesday that represents the largest and most comprehensive analysis of Zika’s consequences for pregnant women.

Women infected during the first trimester of pregnancy had an even higher risk of birth defects, about 15 per cent, according to the analysis by the Centers for Disease Control and Prevention.

The estimates are higher than US health officials have previously reported and underscore the serious risk for birth defects posed by Zika virus infection during pregnancy. With warm weather, a new mosquito season and summer travel approaching, prevention is crucial to protecting the health of mothers and babies, said Anne Schuchat, the CDC’s acting director.

It may seem like Zika is last year’s problem, she said, but that is not true, and pregnant women, their male partners, and clinicians can’t be complacent.

“Don’t let this outbreak be your family’s heartbreak,” she said.

Most infections are spread by mosquitoes, but the virus also can be transmitted through sex and bodily fluids.

Don’t let this outbreak be your family’s heartbreak
Anne Schuchat, the CDC’s acting director

Previous studies of Zika-associated birth defects were based on data from a small number of completed pregnancies. This new report analysed data from nearly 1,000 pregnant women in 44 US states who completed their pregnancies in 2016 and had some evidence of a Zika infection. Most were exposed during travel to one of the dozens of Zika-affected countries.

Of the 972 completed pregnancies, 250 women had confirmed infections. Of those, 24 pregnancies - about 10 per cent - resulted in a foetus or baby with birth defects.

Screening for Zika is difficult because many infected people don’t have symptoms that might motivate them to get tested, and the longer the time lag after infection, the more complicated diagnosis becomes.

Even more disturbing, the risk for birth defects is almost certainly higher than the study suggests, because three-fourths of the infants born to mothers with some evidence of Zika infection did not receive the recommended brain imaging after birth. The link between Zika and birth defects was first noticed because the infection can cause microcephaly, or an abnormally small head. Subsequent research showed that babies may appear healthy at birth, with a normal head size, but have underlying brain abnormalities. Of 895 live births, only 221 babies received any kind of neuroimaging.

“It’s really key for these babies to have a head ultrasound or CT scan to look for abnormalities that may not be apparent at birth,” Margaret Honein, chief of the birth defects branch at the CDC and author of the report, said in an interview. “Knowing that not all these babies are receiving brain imaging, this may be significantly underestimating the complete number of infants with birth defects.”

Honein said she didn’t know why so many babies were not receiving the recommended brain evaluations. The reasons are likely to be complex, she said. All health-care providers, especially obstetricians and pediatricians, need to improve monitoring of these infants. The CDC is monitoring all pregnant women in the United States with any evidence of Zika infection; the agency is receiving 30 to 40 new reports of such pregnancies every week, she said.

Although microcephaly has been the most high-profile birth defect associated with Zika infections, congenital Zika syndrome is associated with a broad range of symptoms. They include eye abnormalities, hearing loss and problems moving limbs.

As a result, some babies have seizures, others have little to no control over their arms and legs, and can’t freely reach out to touch things around them because of constricted joints, Schuchat said during a briefing with reporters. Some babies are not reaching their typical developmental milestones, like sitting up. Others have trouble swallowing or even breathing while feeding. Some babies are often inconsolable no matter what their caregiver does to soothe them.

“We’ve seen that these circumstances are just heartbreaking for families and clinicians,” she said.

The cost for treating an infant with microcephaly is estimated at nearly US$4 million, she said. For those who survive into adulthood, the costs could be up to US$10 million.

Researchers don’t know the full impact of a congenital Zika infection, and for that reason, they want to have the babies followed and evaluated for the first year or two, Honein said.

Honein, co-lead for the CDC Zika Response Team’s Pregnancy and Birth Defects Task Force, said the latest numbers show an undeniable increase in microcephaly and related neurological defects due to Zika.

The rate of 10 per cent reported in the study is more than 30 times higher than the baseline prevalence before 2016, which was about three of every 1,000 live births.