Zika virus in pregnancy

(Date: August 2016. Version: 6)

This factsheet has been written for members of the public by the UK Teratology Information Service (UKTIS). UKTIS is a not-for-profit organisation funded by Public Health England on behalf of UK Health Departments. UKTIS has been providing scientific information to health care providers since 1983 on the effects that medicines, recreational drugs and chemicals may have on the developing baby during pregnancy.

What is it?

Zika virus is an infection that is mainly spread by mosquitos. Zika virus can cause mild flu-like symptoms, a raised temperature, conjunctivitis, joint pain in the hands and feet, and a red pimply rash that often spreads from the face to the body. Symptoms usually appear between 3 and 12 days after a mosquito bite, and last between 2 and 7 days. However, it is thought that only around 1 out of every 4 people infected with Zika virus experience any symptoms.

How can catching Zika virus during pregnancy affect an unborn baby?

There is increasing evidence to suggest that infection with the Zika virus during pregnancy can stop the baby’s brain from forming or growing normally.  As a result, the baby might have a small head (‘microcephaly’), stiffness, and problems with learning and development after birth. 

Studies are currently being carried out to increase our understanding of how Zika virus infection during pregnancy might affect an unborn baby, both in the womb and later on in life. We do not yet know whether only babies who have been exposed to the virus at a specific stage of pregnancy are at risk of developing microcephaly and its associated problems. At present it is thought that the majority of babies who have been born with microcephaly following Zika virus infection in pregnancy have been exposed to the virus in the first trimester (the first 13 weeks of pregnancy). However, there are reports of microcephaly and brain abnormalities in a few babies whose mothers report being possibly infected with Zika virus after the first trimester. We do not yet know how likely a baby is to have problems following Zika virus infection in the mother in pregnancy.

Which areas of the world have been affected by Zika virus?

The reports of Zika virus infection causing microcephaly in babies have mainly come from rural areas of Brazil. Zika virus infection has also been reported in people in many other countries including Barbados, Bolivia, Cape Verde, Columbia, Dominican Republic, Ecuador, El Salvador,  French Guiana, Guadeloupe, Guatemala, Guyana, Haiti, Honduras, Martinique, Mexico, Nicaragua, Panama, Paraguay, Puerta Rico, Saint Martin, Samoa, Suriname, Thailand, Venezuela, and US Virgin Islands.  For an up to date list, see The Public Health England guidance on Zika Virus (click here). However, at present there is very little information as to whether a similar increase in brain abnormalities and microcephaly in babies has been observed in these countries too.

Can I catch Zika virus from insect bites in the UK?

No, the type of mosquito that spreads Zika virus is not present in the UK as the climate is too cool. The reports of UK residents with Zika virus relate to people who have caught the infection while travelling to an area of the world where Zika virus is circulating.

How can I avoid catching Zika virus during pregnancy?

The National Travel Health Network and Centre (NaTHNaC) in the UK has advised pregnant women to consider avoiding travel to areas where Zika virus outbreaks are currently reported. Women who are planning to become pregnant are advised to discuss their travel plans with their healthcare provider to assess their risk of Zika virus infection, and to obtain advice on insect bite avoidance measures (see below). The Centers for Disease Control (CDC) in America also advise pregnant women or women who are trying to become pregnant who are due to travel to an area where Zika virus has been reported to consider postponing their trip.

In addition, the Royal College of Obstetricians and Gynaecologists (RCOG) in the UK has issued guidance which states that women should avoid becoming pregnant whist in an area where Zika virus is circulating, and for a further 8 weeks after returning from their trip (whether they had symptoms of Zika infection or not).

If you are pregnant and cannot avoid travelling to an area affected by Zika virus, you should take strict precautions to avoid mosquito bites. This includes:

• Using DEET to repel mosquitos. The risk to your baby from Zika virus is likely to be far greater than any risk from using a chemical insect repellent in pregnancy. DEET should be reapplied regularly, and should be applied to the skin after any sunscreen, rather than before.

• Staying inside as much as possible during mid-morning and from late afternoon to dusk. The mosquitoes that transmit Zika Virus are mainly active during daylight hours, and most bites occur at these times.

• Covering up exposed skin as much as possible with light coloured, loose fitting clothing (e.g. long sleeves and full length trousers)

• Applying an insecticide that kills mosquitos on contact (such as permethrin) to clothing and mosquito nets

• Using mosquito screens on doors and windows

• Sleeping with mosquito nets over the bed

All of these measures should be used together to minimise the risk of Zika virus infection. It should be noted that the mosquitos that transmit malaria are most active from dusk to dawn. Women travelling to areas where both malaria and Zika virus are circulating are therefore also advised to stay inside as much as possible during these times.

For more information on malaria, avoiding mosquito bites, and use of insect repellents in pregnancy, please see the bump leaflets on malaria prophylaxis and insect repellents.

Can Zika virus affect my unborn baby if I was infected before I became pregnant?

Once you have fully recovered from the symptoms of Zika virus, there is currently no indication that it can affect future pregnancies. Because it can take up to two weeks for an infected person to show symptoms of Zika virus, and a further two weeks to recover from the illness, the Royal College of Obstetricians and Gynaecologists (RCOG) in the UK has stated that as a precaution, women should avoid becoming pregnant for a 8 weeks following travel to an area where Zika virus is circulating.

What should I do if I travelled to an area where Zika virus is circulating whilst pregnant?

If during your pregnancy you have travelled to an area where Zika virus is circulating, you should tell your doctor or midwife as soon as possible.

If you have had recent symptoms of Zika virus, you may be asked to provide blood and/or urine samples that will be tested to see if you have the infection.

In the UK, all pregnant women with confirmed Zika virus, or who have previously shown symptoms of the infection will be referred to a fetal medicine specialist, who is likely to advise monthly ultrasound scans to check growth of the baby’s head in the womb. Pregnant women who have visited an area where Zika virus is circulating but have not shown any symptoms of Zika virus might also be advised to undergo monthly ultrasound scans to check the growth of the baby’s head. This is because the majority of people with Zika virus do not show any symptoms.

It is also important that babies of women who travelled to an area where Zika virus is circulating during their pregnancy are checked at birth for features of Zika infection in the womb as some may not be detectable on ultrasound scans.

What if am pregnant or could become pregnant and my sexual partner had Zika virus or travelled to an area where the virus is circulating?

Zika virus can persist in semen (sperm) even after a man has recovered from the symptoms of the illness. Some reports have suggested that the virus can be sexually transmitted, although the chance of this is thought to be very small. There is therefore a risk that Zika virus could be passed to a woman (and an unborn baby) via unprotected sexual contact with an infected partner. The Royal College of Obstetricians and Gynaecologists (RCOG) in the UK has therefore issued guidance which states that if a male traveller has visited an area where Zika virus is circulating:

• Effective contraception to prevent pregnancy, and condoms to prevent viral transmission should be used for 8 weeks after return if they showed no symptoms of Zika virus.
• Effective contraception to prevent pregnancy, and condoms to prevent viral transmission should be used for 6 months after recovery if they showed symptoms of Zika virus or had confirmed Zika infection.
• Condoms should be used for the remainder of the pregnancy if their partner is already pregnant.

If you know that your partner had Zika virus while you were pregnant and might have passed this on to you through sexual contact, even if you did not have any symptoms, you should speak to your doctor or midwife who might advise extra monitoring of your baby.

Where can I find more information about Zika virus and pregnancy?

New advice and information about Zika virus and pregnancy is being released, sometimes on a daily basis. It is important to check the latest advice, particularly regarding the areas where outbreaks of Zika virus have currently been reported. Useful websites include the European Centre for Disease Prevention and Control (ECDC) (click here), the Travel Health Pro website (click here) , the American CDC website (click here) and the American Medical Association (click here).

Who can I talk to if I have questions?

If you have any questions regarding the information in this leaflet please discuss them with your health care provider. They can access more detailed medical and scientific information on insect repellents from www.uktis.org.  

General information 

Up to 1 out of every 5 pregnancies ends in a miscarriage, and 1 in 40 babies are born with a birth defect. These are referred to as the background population risks.  They describe the chance of these events happening for any pregnancy before taking factors such as the mother’s health during pregnancy, her lifestyle, medicines she takes and the genetic make up of her and the baby’s father into account.

Medicines use in pregnancy

Most medicines used by the mother will cross the placenta and reach the baby. Sometimes this may have beneficial effects for the baby.  There are, however, some medicines that can harm a baby’s normal development.  How a medicine affects a baby may depend on the stage of pregnancy when the medicine is taken. If you are on regular medication you should discuss these effects with your doctor/health care team before becoming pregnant.

If a new medicine is suggested for you during pregnancy, please ensure the doctor or health care professional treating you is aware of your pregnancy.

When deciding whether or not to use a medicine in pregnancy you need to weigh up how the medicine might improve your and/or your unborn baby’s health against any possible problems that the drug may cause. Our bumps leaflets are written to provide you with a summary of what is known about use of a specific medicine in pregnancy so that you can decide together with your health care provider what is best for you and your baby.   

Every pregnancy is unique. The decision to start, stop, continue or change a prescribed medicine before or during pregnancy should be made in consultation with your health care provider. It is very helpful if you can record all your medication taken in pregnancy in your hand held maternity records.



Disclaimer: This information is not intended to replace the individual care and advice of your health care provider. New information is continually becoming available. Whilst every effort will be made to ensure that this information is accurate and up to date at the time of publication, we cannot cover every eventuality and the information providers cannot be held responsible for any adverse outcomes following decisions made on the basis of this information. We strongly advise that printouts should NOT be kept for any length of time, or for “future reference” as they can rapidly become out of date.

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