Birth Defects Seen in One in 10 Zika-infected Pregnancies

CDC Officials Call for Physicians to Remain Vigilant

April 05, 2017 03:15 pm News Staff

Of the 250 U.S. women who had laboratory-confirmed Zika infection during pregnancy in 2016, 24 -- or about one in 10 of them -- had a fetus or baby with Zika-related birth defects.

That's according to a CDC Morbidity and Mortality Weekly Report(www.cdc.gov) and an accompanying Vital Signs report(www.cdc.gov) released April 4.

"Zika virus can be scary and potentially devastating to families. Zika continues to be a threat to pregnant women across the U.S.," said CDC Acting Director Anne Schuchat, M.D., in a news release.(www.cdc.gov)
"With warm weather and a new mosquito season approaching, prevention is crucial to protect the health of mothers and babies. Health care providers can play a key role in prevention efforts."

The reports are the first to analyze the subset of pregnant women in the United States who had laboratory-confirmed Zika virus infection.

Story highlights
  • One out of 10 pregnant women in the United States with confirmed Zika infection in 2016 had a fetus or infant with Zika-related birth defects.
  • During the 2016 time period analyzed, 1,297 pregnant women in 44 states were reported to the CDC's U.S. Zika Pregnancy Registry, including 972 with completed pregnancies comprising 895 live births and 77 pregnancy losses.
  • Among pregnancies with confirmed Zika virus infection, brain abnormalities and/or microcephaly were reported in 75 percent of fetuses and infants with birth defects.

Analysis Methodology

Early last year, the CDC established the U.S. Zika Pregnancy Registry (USZPR) in collaboration with state, tribal, local and territorial health departments to monitor pregnant women with laboratory evidence of possible recent Zika virus infection and their infants.

The CDC reports are based on an analysis of completed pregnancies (including live births and pregnancy losses, regardless of gestational age) in the 50 states and the District of Columbia with laboratory evidence of possible recent Zika virus infection reported to the USZPR from Jan. 15 to Dec. 27, 2016.

Zika virus-associated birth defects were analyzed in two mutually exclusive categories:

  • brain abnormalities and/or microcephaly regardless of the presence of additional birth defects; and
  • neural tube defects and other early brain malformations, eye abnormalities and other consequences of central nervous system dysfunction, among fetuses and infants without evident brain abnormalities or microcephaly.

Clinical experts reviewed reported information to ensure that each fetus or infant with birth defects met the criteria of the USZPR case definition.

Key Findings From Report

During the 2016 time period analyzed, 1,297 pregnant women in 44 states were reported to the USZPR, including 972 completed pregnancies comprising 895 live births and 77 pregnancy losses.

The CDC plans to update its Zika virus resources periodically, including this April 4 Vital Signs report factsheet.

Among women with completed pregnancies, about 62 percent were asymptomatic, about 36 percent were symptomatic, and about 3 percent had missing symptom information. For symptomatic women, gestational timing of Zika virus infection was calculated using symptom onset date. For asymptomatic women, the trimester of exposure was calculated using dates of travel to areas with active Zika virus transmission or sexual exposure.

Zika virus-associated birth defects were reported for about 5 percent of fetuses and infants from completed pregnancies with laboratory evidence of possible recent Zika infection. Birth defects were reported in 15 percent of fetuses and infants of completed pregnancies with confirmed Zika virus infection during the first trimester.

Among pregnancies with confirmed Zika virus infection, brain abnormalities and/or microcephaly were reported in 75 percent of fetuses and infants with birth defects.

NIH Begins Phase 2 Zika Vaccine Trial

Vaccinations have begun in a multisite Phase 2/2b clinical trial that's testing an experimental DNA vaccine designed to protect against disease caused by Zika infection. Scientists at NIH's National Institute of Allergy and Infectious Diseases (NIAID) developed the vaccine.

NIAID is leading the two-part trial, called VRC 705, which aims to enroll at least 2,490 healthy participants in areas of confirmed or potential active mosquito-transmitted Zika infection, including the continental United States and Puerto Rico, Brazil, Peru, Costa Rica, Panama and Mexico.

"We are pleased to have advanced rapidly one of NIAID's experimental Zika vaccines into this next stage of testing in volunteers. We expect this study will yield valuable insight into the vaccine's safety and ability to prevent disease caused by Zika infection," said NIAID Director Anthony Fauci, M.D., in a news release.(www.nih.gov)

The 51 fetuses or infants with birth defects were from pregnancies involving Zika virus exposure associated with the following 16 countries/territories with active Zika virus transmission: Barbados, Belize, Brazil, Cape Verde, Colombia, Dominican Republic, El Salvador, Guatemala, Guyana, Haiti, Honduras, Jamaica, Mexico, Puerto Rico, Republic of Marshall Islands and Venezuela.

Among the nearly 900 live births from pregnancies with possible recent Zika virus infection, postnatal neuroimaging was reported for only about 25 percent, and Zika virus testing of at least one infant specimen was conducted in 65 percent of these patients.

The CDC said these findings confirm the serious threat Zika virus infection poses during pregnancy and the critical need for pregnant women to avoid Zika virus exposure through mosquito bites and sexual transmission.

Family Physicians Can Help

The report emphasized the importance of physicians screening all pregnant women for possible Zika virus exposure at every prenatal visit, and testing and evaluating all infants born to women with evidence of Zika infection in accordance with current CDC guidance.(www.cdc.gov)

Identification and follow-up care of infants born to mothers with laboratory evidence of possible recent Zika virus infection during pregnancy and infants with possible congenital Zika virus infection can help ensure that appropriate intervention services are available to affected infants, the MMWR report concluded.

"Based on reports to the registry, many babies born to mothers with possible Zika infection are not receiving brain imaging after birth to help diagnose serious brain defects," said Peggy Honein, Ph.D., co-lead of the Pregnancy and Birth Defects Task Force that is part of CDC's Zika response team, in the release. "Health care providers have an important role, and we encourage them to ask about possible Zika exposure when caring for both pregnant women and their babies, and to follow CDC guidance for evaluation and care of infants with possible Zika infection."

The CDC said it will continue to update its guidance for health care professionals on testing and clinical care for pregnant women and infants affected by Zika virus. The agency said it also is monitoring new infections and working to identify the long-term outcomes of congenital Zika infection.

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AAFP, Other Groups to Congress: Continue to Fund Fight Against Zika
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Texas Announces Possible Local Mosquito-transmitted Zika Case
CDC Reports on Evidence of Microcephaly Developing After Birth

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Utah Zika Case Points to Likely New Transmission Route
CDC Updates Interim Guidance, Expands Travel Advisory

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