SUMMARY:

On July 24, 2017, the CDC released interim guidance on management of pregnant women with possible Zika exposure.  The CDC based this update on (1) declining prevalence of Zika virus disease in the WHO’s Region of the Americas (Americas) and (2) evidence of prolonged detection of Zika virus IgM antibodies beyond 12 weeks after infection, thus limiting an IgM test’s ability to distinguish whether an infection has occurred before or during the pregnancy.

• ‘Exposure’ definition
• Asking about exposure
• Symptomatic with recent exposure
• Asymptomatic with ongoing exposure
• Additional Zika testing following diagnosis
• Asymptomatic without ongoing exposure
• Suspicious prenatal fetal ultrasound
• Pregnant with laboratory evidence of possible Zika
• Testing placental and fetal tissues
• IgM baseline preconception testing

KEY POINTS:

The definition of ‘possible Zika virus exposure’ is unchanged and still includes

• 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

Ask all pregnant women in the US and US territories about possible Zika virus exposure before pregnancy and again at every prenatal visit

• Pregnant women should be advised not travel to any area with risk for Zika virus transmission
• Pregnant women with a sex partner who has traveled to or lives in an area with risk for Zika virus transmission should be advised on the use condoms or abstain from sex for the duration of the pregnancy

Testing pregnant women with recent possible Zika virus exposure and symptoms

• Symptoms include acute onset of fever, maculopapular rash, arthralgia, or conjunctivitis
• Recent exposure is defined as a possible exposure or infection during the current pregnancy or 8 weeks before conception or 6 weeks before the last menstrual period
• Updated recommendations include concurrent Zika virus NAT and serologic testing as soon as possible through 12 weeks after symptom onset

Testing pregnant women who are asymptomatic with ongoing possible Zika virus exposure

• Ongoing possible Zika virus exposure includes those who reside in or travel frequently (e.g., daily or weekly) to an area with risk for Zika virus transmission
•  Offer Zika virus NAT testing three times during pregnancy
  • NAT testing should be offered at the initiation of prenatal care, and if Zika virus RNA is not detected on clinical specimens, two additional tests should be offered during the course of the pregnancy coinciding with prenatal visits
• IgM testing is no longer routinely recommended because IgM can persist for months after infection
• The optimal timing and frequency of testing of asymptomatic pregnant women with NAT alone is unknown

Additional Zika testing is not recommended following laboratory–confirmed Zika virus infection diagnosis that has been made before or during the current pregnancy

• Diagnosis is laboratory-confirmed by one of the following:
  • NAT, or
  • Serology: positive/equivocal Zika virus or dengue virus IgM and Zika virus plaque reduction neutralization test (PRNT) ≥10 and dengue virus PRNT <10 results

Testing pregnant women who are asymptomatic who have recent possible Zika exposure (travel or sexual exposure) but without ongoing possible Zika virus exposure

• Routine Zika virus testing is not recommended
• Testing should be considered using a shared patient-provider decision-making model based on patient preferences and values, clinical judgment, a balanced assessment of risks and expected outcomes, and the jurisdiction’s recommendations
• With the decline in the prevalence of Zika virus disease, the updated recommendations for the evaluation and testing of pregnant women with recent possible Zika virus exposure but without ongoing possible exposure are now the same for all areas with any risk for Zika virus transmission

Testing pregnant women who have recent possible Zika virus exposure and who have a fetus with prenatal ultrasound findings consistent with congenital Zika virus syndrome 

• Test for Zika virus to determine the etiology of the birth defects
• Testing of the mother should include both NAT and IgM tests
• Possible Zika virus–associated birth defects that meet the CDC surveillance case definition include the following:
  • Brain abnormalities and/or microcephaly
  • Intracranial calcifications
  • Ventriculomegaly
  • Neural tube defects and other early brain malformations
  • Eye abnormalities
  • Other consequences of central nervous system dysfunction including arthrogryposis (joint contractures), congenital hip dysplasia, and congenital deafness
• Individualize the use of amniocentesis
  • Limited data on usefulness
  • NAT testing should be performed on amniocentesis specimens
  • Zika virus RNA in the amniotic fluid might indicate fetal infection but a negative result does not exclude congenital Zika virus infection
  • Optimal time to perform amniocentesis to diagnose congenital Zika virus infection is unknown

Updated Interim Guidance for Prenatal Management of Pregnant Women with Laboratory Evidence of Possible Zika Virus Infection

• Serial fetal ultrasounds every 3 to 4 weeks with focus on neuroanatomy and growth
• Recent data suggests a period of at least 15 weeks between infection and microcephaly detection on prenatal ultrasound and MRI
• Based on 17 cases with confirmed prenatal maternal Zika virus
  • Median time between Zika virus symptoms and microcephaly was 18 weeks (range 15–24 weeks)
  • Earliest sign of congenital Zika syndrome was clubfoot
  • MRI findings: microcephaly, ventriculomegaly, polymicrogyria, and calcifications

The comprehensive approach to testing placental and fetal tissues has been updated

• Testing placental and fetal tissue specimens can be performed for diagnostic purposes in certain scenarios
• Example of a possible scenario: A fetus or infant with possible Zika virus-associated birth defects but maternal definitive diagnosis is not available
• In all cases, infants or fetuses with possible Zika virus–associated birth defects should also be evaluated for other etiologies of congenital anomalies
• Testing of placental tissues for Zika virus infection is not routinely recommended for asymptomatic pregnant women who have recent possible Zika virus exposure but without ongoing possible exposure and who have a live born infant without evidence of possible Zika virus–associated birth defects

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

• Zika virus IgM testing is no longer routinely recommended for asymptomatic pregnant women with ongoing possible Zika virus exposure

Learn More – Primary Sources:

Update: Interim Guidance for Health Care Providers Caring for Pregnant Women with Possible Zika Virus Exposure — United States (Including U.S. Territories), July 2017 

CDC: Zika Virus For Healthcare Providers

CDC: Areas with Risk of  Zika

PAHO: Regional Zika Epidemiological Update (Americas)

Serial Head and Brain Imaging of 17 Fetuses With Confirmed Zika Virus Infection in Colombia, South America

US Zika Pregnancy Registry Collaboration: Birth Defects Among Fetuses and Infants of US Women With Evidence of Possible Zika Virus Infection During Pregnancy

ACOG and SMFM Practice Advisory Interim Guidance for Care of Obstetric Patients During a Zika Virus Outbreak

ACOG Zika Tool Kit 

Related ObG Topics:

Zika virus: transmission, symptoms and management

New CDC Interim Guidance on Infants with Possible Zika & Perinatal Review (Oct 2017)

Zika Virus Disease: How to Counsel Your Patient About Prevention

Microcephaly – Beyond the Zika Virus

CDC Guidance for Non-Pregnant Patients and Available Diagnostic Tests for Zika Virus

Prenatal Detection of Clubfoot – Key Points