Zika virus

(Date: February 2023. Version: 8)

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 the UK Health Security Agency (UKHSA) 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.

Quick read

Zika virus can harm an unborn baby. Pregnant women should avoid travel to affected areas and unprotected sex with a partner who has recently travelled to such an area. If travel is essential, women should take strict measures to avoid mosquito bites.

What is it?

Zika virus is an infection which is mainly spread by mosquitos and can also be passed on through sex. In most cases, Zika virus causes no symptoms, and many people are not aware they have it. Zika can also cause mild flu-like symptoms, sore eyes and/or a rash. If caught in pregnancy, Zika virus can harm the unborn baby.

How might Zika virus affect an unborn baby?

Infection with Zika virus during pregnancy can stop the baby’s brain from forming and growing normally. As a result, the baby may be born with disabilities linked to altered brain development and may have a small head (microcephaly) and problems with hearing, learning and behaviour. Zika virus has also been linked to pregnancy loss. The highest risk of these problems is after having Zika infection in the first trimester.

How can I avoid catching Zika virus during pregnancy?

Pregnant women can avoid Zika virus by:

  • Avoiding travel to areas where there are high levels of Zika virus.
  • Avoiding unprotected sex for the rest of the pregnancy with a partner who has recently had Zika virus or travelled to an area with Zika virus.

If travel to an area with Zika cannot be avoided, strict measures to avoid mosquito bites should be taken, including:

  • Using the insect repellent DEET on the skin. Other types of insect repellent are less effective and should not be used.
  • 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.
  • 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.

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

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

The information about Zika virus and pregnancy is updated regularly. It is important to check the latest advice, particularly regarding high-risk areas. Useful websites include the Travel Health Pro website and the American CDC website. For more information on exposure to Zika virus in pregnancy there is a useful factsheet from the UK Health Security Agency.

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

How can I help to improve drug safety information for pregnant women in the future?

Our online reporting system allows women with a current or previous pregnancy to create a digitally secure ‘my bumps record’. You will be asked to enter information about your health, whether or not you take any medicines, and your pregnancy outcome. You can update your details at any time during pregnancy or afterwards. This information will help us better understand how medicines affect the health of pregnant women and their babies. Please visit https://www.medicinesinpregnancy.org/Login/ to register.


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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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