(Date: February 2019. Version: 3)

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.

What is it?

Mefloquine is a medicine that is taken either on its own or more commonly in combination with another medicine to:
• prevent malaria infection (for example, before travelling to a part of the world where the chance of being infected with malaria is high) 
• treat a person who has been infected with malaria 

Malaria is a serious illness that is spread by mosquito bites and can result in death. Malaria infection in pregnancy can be dangerous to both mother and baby. Pregnant women are therefore advised to avoid travelling to areas where there is a risk of catching malaria. If you are pregnant or planning a pregnancy and cannot avoid travelling to a high risk malaria area, ask your doctor for advice as soon as possible. You may need to start taking an antimalarial medicine a few weeks before you travel. Your doctor is the best person to help you decide what is right for you and your baby.

Is it safe to take mefloquine in pregnancy?

If you are travelling to certain regions you may be advised to take mefloquine. This is because in some areas other anti-malarial medicines are ineffective. You should not avoid taking mefloquine just because you are pregnant. The risk of harm to you and your baby from malaria is far greater than any potential risk from taking mefloquine.

No antimalarial medicine is 100% effective and it is very important that you also reduce the chance of being bitten by using insect repellents, mosquito nets, and covering as much skin as possible with clothing, particularly between dawn and dusk. Please read our bumps leaflet on insect repellents for more information on which products are advised for use in pregnancy.

Can taking mefloquine in pregnancy cause miscarriage?

There is currently no evidence that mefloquine use in pregnancy causes miscarriage.

Eleven studies investigated the chance of miscarriage with mefloquine use. In nine of these studies no link with miscarriage was seen. One study looked at front-line soldiers who took mefloquine, however the miscarriage rate may be higher in this population due to factors other than medicine use. The other study showed a slight increase in miscarriage following use of mefloquine compared to other antimalarial drugs, but women taking mefloquine still had a similar chance of miscarriage as women in the background population.

Overall, the studies on the chance of miscarriage in women taking mefloquine during pregnancy are reassuring, but more information on pregnant women taking mefloquine is needed.

Can taking mefloquine in pregnancy cause my baby to be born with birth defects?

A baby’s body and most internal organs are formed during the first 12 weeks of pregnancy. It is during this time that some medicines are known to cause birth defects.

No studies suggest that women who take mefloquine in early pregnancy have a higher chance of having a baby with a birth defect.

Can taking mefloquine in pregnancy cause preterm birth?

Mefloquine use in pregnancy has not been shown to cause a baby to be born early in any of three studies. Malaria infection has been linked to preterm birth.

Can taking mefloquine in pregnancy cause my baby to be small at birth (low birth weight)?

No increased chance of low birth weight was seen in four out of the five studies of babies born to pregnant women taking mefloquine. Although one study did suggest a possible link with low birth weight, this study included pregnant women with malaria which is itself known to cause low birth weight in the baby.

Can taking mefloquine in pregnancy cause stillbirth?

No increased chance of stillbirth was seen in four out of the five studies of pregnant women taking mefloquine. Although one study did suggest a possible link, this study included women with malaria which is itself known to increase the chance of stillbirth.

Can taking mefloquine in pregnancy cause learning or behavioural problems in the child?

A baby’s brain continues to develop right up until the end of pregnancy. It is therefore possible that taking certain medicines at any stage of pregnancy could have a lasting effect on a child’s learning or behaviour. Because use of mefloquine has been linked to long-term neurological and mental health problems in some people, it has been questioned whether mefloquine might hypothetically affect the development of an unborn baby’s brain. It has also been suggested that malaria infection during pregnancy might affect a baby’s developing brain, but this too remains to be confirmed.

There is no evidence so far that mefloquine use in pregnancy causes learning or behavioural problems in the child. Four studies have all shown no difference in the age at which children who were exposed to mefloquine while in the womb reached key developmental milestones (such as sitting, walking and talking) compared to unexposed children.

Will my baby need extra monitoring during pregnancy?

As part of their routine antenatal care, most women will be offered a scan at around 20 weeks of pregnancy to look for birth defects and to check the baby’s growth.

Taking mefloquine during pregnancy is not expected to cause any problems that would require extra monitoring of your baby. However, if you have been infected with malaria during your pregnancy your doctor may wish to monitor your pregnancy more closely.

Are there any risks to my baby if the father has taken mefloquine?

We would not expect any increased risk to your baby if the father took mefloquine before or around the time your baby was conceived.

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 from

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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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