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Zika virus

Zika virus is a mosquito-borne infection which has been associated with profound effects on the unborn fetus in pregnant women. It was first reported in Africa in the 1940s but prior to the major outbreak in Brazil in 2015, few outbreaks have been documented. It has since spread rapidly over most countries in South and Central America and the Caribbean. The majority of people infected with Zika virus have no symptoms, but where they occur, they include: rash, itching/pruritis, fever, headache, arthralgia and myalgia. The illness tends to be mild and self-limiting within 2 - 7 days. The major concern is that Zika virus is a cause of microcephaly and other congenital anomalies (congenital Zika syndrome). Zika can cross the placental barrier, and it is likely that infection in early pregnancy poses the greatest risk. Pregnant women who have recently travelled in an area reporting active Zika virus transmission in the last 9 months should seek advice from their midwife on their return to the UK, even if they have not been unwell. A detailed travel history should be undertaken.

Testing for the virus is by reverse transcription polymerase chain reaction (RT-PCR) on a maternal blood sample. The test may also be performed on a sample of amniotic fluid, after careful assessment of the risk of miscarriage or preterm birth, although it is not known how sensitive this test is for congenital infection or the likelihood of an infected fetus subsequently developing a fetal abnormality.

Where the virus is detected on laboratory testing, the woman should be referred to a fetal medicine service for further assessment. If the test result is negative, serial (4-weekly) fetal ultrasound scans should be considered to monitor fetal growth and anatomy. If a significant brain abnormality or microcephaly is confirmed (by fetal brain MRI) the option of termination of pregnancy should be discussed with the woman, regardless of gestation.

Following birth

Following a live birth where there has been laboratory confirmation of maternal or fetal Zika virus infection, the following tests are recommended:

  • Histopathological examination of the placenta and umbilical cord
  • Testing of placental tissue and cord tissue for Zika virus RNA
  • Testing of cord blood and neonatal urine for Zika virus and other flaviviruses.

If congenital infection is subsequently confirmed, the baby should be followed up into childhood for signs of any adverse sequelae.

N.B. Guidance on Zika virus is evolving rapidly and midwives should ensure they access the most up-to-date advice.

Further reading

Public Health England (2016). Zika virus: Clinical advice on Zika: assessing pregnant women following travel; symptoms, transmission (includes sexual transmission), epidemiology.

The Royal College of Midwives (2016). The latest Zika virus advice for March.

Royal College of Obstetricians & Gynaecologists, Royal College of Midwives, Public Health England, Health Protection Scotland (2016). Interim RCOG/RCM/PHE/HPS clinical guidelines: Zika Virus infection and Pregnancy. Information for Healthcare professionals.


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