Zika virus in pregnancy

(Date: October 2017. Version: 7)

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 mosquitoes. Sexual transmission has also been reported. 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?

Infection with Zika virus during pregnancy can stop the baby’s brain from forming normally or growing at the correct rate. As a result, the baby might have a small head (microcephaly), muscle stiffness, and/or problems with learning and development after birth.

The most up-to-date evidence suggests that around 1 in every 10 babies whose mothers had Zika virus in the first trimester of pregnancy may be born with these types of birth defects. Zika virus infection in the second and third trimesters can also cause these problems in the baby.

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

The reports of Zika virus infection causing microcephaly in babies initially came from rural areas of Brazil. Zika virus infection has since been reported in many other countries.

Areas with current or previous Zika virus transmission have now been rated as high, moderate, or low risk to travellers. The greatest chance of catching Zika virus is in a place with high to moderate risk, although the chance of catching the infection can be reduced by avoiding mosquito bites (see below). For an up-to-date list of countries and areas and their risk ratings visit the Public Health England (PHE) website.

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 that:
• Pregnant women should avoid visiting areas rated as high risk and consider avoiding travel to moderate risk areas
• Pregnant women whose male partner has visited a high or moderate risk area should use condoms (or another effective barrier method) during all sexual contact for the remainder of the pregnancy
• Women who are planning a pregnancy should consider delaying conception for at least eight weeks following return from a high or moderate risk area. Women whose male partner has travelled to a high or moderate risk area should avoid conception for six months following his return and should ideally ensure that condoms (or another effective barrier method) are used during all sexual contact
• All travellers to high, moderate, and low risk areas should employ strict measures to prevent mosquito bites

How do I avoid mosquito bites?

Measures that can be used to avoid mosquito bites include:
• Using DEET to repel mosquitoes. 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 mosquitoes 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 mosquitoes that transmit malaria are most active from dusk to dawn. People 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. NaTHNaC recommends that women who have had symptoms of Zika virus should avoid becoming pregnant for 8 weeks after symptoms started.

What should I do if I travelled to a high, moderate, or low risk area while pregnant?

If during your pregnancy you have travelled to a high or moderate risk area you should contact your GP on return to the UK, even if you have not been unwell.

If you have travelled to a low risk area and have experienced symptoms of Zika virus infection you should also contact your GP on your return.

In these instances you may be referred to a fetal medicine specialist who is likely to advise additional ultrasound scans to check growth of the baby’s head in the womb.

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

Where can I find more information about Zika virus and pregnancy?
The advice and information about Zika virus and pregnancy is being updated regularly. It is important to check the latest advice, particularly regarding high, moderate, and low risk areas. Useful websites include the Travel Health Pro website and the American CDC website.

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.  

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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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