Updated
September 25th, 2019

Pregnant Women Testing for Zika Updated

Zika tests detecting immunoglobulin B (IgM) antibodies may yield false positive results

The Centers For Disease Control and Prevention (CDC) has updated its guidance for pregnant women with possible exposure to Zika virus.

Although the understanding of the consequences of Zika virus infection is improving, diagnosing Zika virus infection accurately continues to present challenges.

This CDC update includes separate recommendations for pregnant women with Zika symptoms and pregnant women without symptoms.

The change focuses on one of the most frequently used Zika tests which detects immunoglobulin B (IgM) antibodies and is more likely to yield a false positive test result.

Recent studies have found that Zika IgM antibodies might be detected for months after infection, limiting the ability to tell if the infection occurred before or during pregnancy.

The CDC emphasized that healthcare providers should continue to ask pregnant women at each prenatal visit about possible Zika exposure, such as international travel to known ‘Zika-hot-zones’.

Nucleic acid and serologic testing are still recommended by the CDC for symptomatic pregnant women within 12 weeks of illness onset.

However, for asymptomatic women with ongoing possible exposure, the CDC no longer routinely recommends the IgM testing, due to the test's limitations and difficulty interpreting results.

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Testing placental and fetal tissue specimens can be performed for diagnostic purposes in certain scenarios, such as women without a diagnosis of laboratory-confirmed Zika virus infection and who have a fetus or infant with possible Zika virus-associated birth defects.

But, testing of placental tissues for Zika virus infection is not routinely recommended for asymptomatic pregnant women who have recent possible Zika virus exposure, without ongoing possible exposure and who have a live born infant without evidence of possible Zika virus–associated birth defects.

During 2015–2016, 47 countries and territories in the Americas reported Zika virus outbreaks. As of July 11, 2017, Pregnant Women with Any Lab Evidence of Zika Virus Infection:

  • US States and DC: 2,047
  • US Territories: 4,285

These numbers reflect the number of pregnancies with laboratory evidence of possible Zika virus infection that have been reported to the pregnancy surveillance systems.

Zika virus is a mosquito-borne flavivirus that is closely related to dengue, West Nile, Japanese encephalitis, and yellow fever viruses.

There is no specific medicine or vaccine for Zika virus.