CDC Updates Guidance on Zika Testing for Pregnant Women

Agency No Longer Advises Routine Testing in Asymptomatic Women Without Ongoing Exposure

July 31, 2017 01:37 pm News Staff

On July 24, the CDC issued an early-release Morbidity and Mortality Weekly Report (MMWR)(www.cdc.gov) updating its interim guidance for health care professionals caring for pregnant women who have possible Zika virus exposure.

[Gloved hand holding blood-filled vial over test result form with Zika virus checked]

According to the MMWR, the dropping prevalence of Zika virus disease in the Americas since last year, plus new evidence indicating that Zika virus immunoglobulin M (IgM) antibodies can be detected far longer than previously thought, prompted the update.

Specifically, as the prevalence of Zika disease falls, the likelihood of false-positive test results rises. Additionally, emerging epidemiologic and laboratory data suggest that Zika virus IgM antibodies can persist longer than 12 weeks after initial infection. As a result, IgM testing can't always distinguish between infections that occurred during a current pregnancy and those that occurred before the pregnancy. Thus, the CDC no longer recommends routine IgM testing.

Story highlights
  • On July 24, the CDC issued an early-release Morbidity and Mortality Weekly Report (MMWR) updating its interim guidance for health care professionals caring for pregnant women with possible Zika virus exposure.
  • The agency noted in the MMWR that the prevalence of Zika virus disease in the Americas has declined significantly since last year, increasing the likelihood of false-positive test results.
  • Additionally, emerging epidemiologic and laboratory data indicate that Zika virus immunoglobulin M (IgM) test results can't always distinguish between infections that occurred during or before a current pregnancy, and the CDC no longer recommends routine IgM testing.

The agency urged physicians to consider these limitations when counseling pregnant women about the risks and benefits of testing for Zika virus infection during pregnancy.

"This updated guidance emphasizes a shared decision-making model for testing and screening pregnant women, one in which patients and providers work together to make decisions about testing and care plans based on patient preferences and values, clinical judgment, and a balanced assessment of risks and expected outcomes," said the MMWR.

It's important to note that the CDC's definition of possible Zika virus exposure(www.cdc.gov) -- that is, from "travel to, or residence in an area with risk for mosquito-borne Zika virus transmission, or sex with a partner who has traveled to or resides in an area with risk for mosquito-borne Zika virus transmission" -- remains unchanged.

The CDC's MMWR offered the following key recommendations:  

  • All pregnant women in the United States and U.S. territories should be asked at every prenatal care visit about possible Zika virus exposure before and during the current pregnancy.
  • Pregnant women with recent possible Zika virus exposure and symptoms of Zika virus disease(www.cdc.gov) should be tested to determine the cause of their symptoms. The revised guidance calls for concurrent Zika virus nucleic acid test (NAT) and serologic testing as soon as possible through 12 weeks after symptom onset.
  • Asymptomatic pregnant women with ongoing possible Zika virus exposure(www.cdc.gov) should be offered Zika virus NAT testing three times during pregnancy. The optimal timing and frequency of such testing is unknown.
  • Asymptomatic pregnant women who have recent possible Zika virus exposure but no ongoing possible exposure are not routinely recommended to have Zika virus testing.
  • Pregnant women with recent possible Zika virus exposure who have a fetus with prenatal ultrasound findings consistent with congenital Zika virus syndrome should receive Zika virus testing to help establish the etiology of the birth defects. Testing in this instance should include both NAT and IgM testing.

AAFP Reschedules Zika Update Webinar

The AAFP's free members-only webinar Zika Virus: Updated Guidance and Recommendations for Family Physicians has been rescheduled to Aug. 10 from 11 a.m. to noon CDT. The webinar's release was postponed to include the updated interim guidance for health care professionals released in the CDC's Morbidity and Mortality Weekly Report (MMWR) on July 24.

Physicians should also note that the comprehensive approach to testing placental and fetal tissues has been updated. Specifically, testing placental and fetal tissue specimens may be performed for diagnostic purposes in certain instances (e.g., women with no laboratory-confirmed Zika virus infection diagnosis who have a fetus or infant with possible Zika virus-associated birth defects). However, placental tissue testing is not routinely recommended for asymptomatic pregnant women with recent possible Zika virus exposure but no ongoing possible exposure who have a live-born infant without evidence of possible Zika virus-associated birth defects.

Furthermore, Zika virus IgM testing as part of preconception counseling to establish baseline IgM results for nonpregnant women with ongoing possible Zika virus exposure is not warranted because Zika virus IgM testing is no longer routinely recommended for asymptomatic pregnant women with ongoing possible exposure.

Finally, the CDC noted that because the updated recommendations will likely reduce routine Zika virus testing for asymptomatic pregnant women with recent possible Zika virus exposure but without ongoing possible exposure, it is critically important for health care professionals to inquire about possible maternal and congenital Zika virus exposure for every newborn. Infants born to mothers with possible Zika virus exposure during pregnancy who did not undergo testing should receive a comprehensive physical examination, including standardized measurement of head circumference and a newborn hearing screen, as part of their routine care.

The agency said it will continue to evaluate all available evidence on the virus and will update its recommendations as new information becomes available.

Related AAFP News Coverage
Birth Defects Seen in One in 10 Zika-infected Pregnancies
CDC Officials Call for Physicians to Remain Vigilant
(4/5/2017)

More From AAFP
Zika Virus Outbreak

Additional Resource
CDC Zika Virus Update(www.cdc.gov)