(Date: October 2014. Version: 2.1b)

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.

Feedback request 

WE NEED YOUR HELP! Do you have 3 minutes to complete a short, quick and simple 12 question user feedback form about our bumps information leaflets? To have your say on how we can improve our website and the information we provide please visit

What is it?

Mefloquine (Lariam®) 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 the health of 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 specifically advised to take mefloquine. This is because in some areas, other anti-malarial medicines are ineffective because the malaria parasite has developed resistance to them. You should not avoid taking mefloquine just because you are pregnant. The risk of harm to you and your baby from malaria is likely to be 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 dusk and dawn. 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 convincing scientific evidence that mefloquine use in pregnancy causes miscarriage. Miscarriage rates have been investigated in studies of ten different groups of women who took mefloquine during pregnancy. In eight of these groups, no increased risk of miscarriage was seen.

One of the two studies that did suggest a possible link between mefloquine and miscarriage showed that female front-line soldiers taking mefloquine had a higher rate of miscarriage than women in the general population. The researchers emphasise that female army personnel may be at increased risk of miscarriage for other reasons related to their work. Additionally, because women in the army are regularly tested for pregnancy they are more likely to recognise their pregnancies earlier, and will therefore be more aware of having a miscarriage than women in the general population who may think that they have simply had a slightly heavier or later period than usual. It is therefore possible that the increased rate of miscarriage observed in this study may be explained by factors not related to mefloquine.

The second study which showed a higher rate of miscarriage in women taking mefloquine compared to women taking a different antimalarial medicine still found that the miscarriage rate amongst women taking mefloquine was no greater than the miscarriage rate in the general population.

Overall, the studies on miscarriage rates in women taking mefloquine during pregnancy are therefore reassuring, but more information on pregnant women taking mefloquine needs to continue to be collected.

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 mainly during this time that some medicines are known to cause birth defects.

There is no convincing scientific evidence to suggest that women who take mefloquine in pregnancy are at an increased risk of having a baby with a birth defect from any of the five studies that have investigated this. However, only a small number of women who took mefloquine during the first three months of pregnancy have been studied and more research is therefore required.

Can taking mefloquine in pregnancy cause preterm birth?

Mefloquine use in pregnancy has not been shown to cause a baby to be born early, although two studies have shown that preterm birth is more common in pregnant women with malaria infection.   

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

Mefloquine use in pregnancy has not been shown to cause a baby to be smaller than expected at birth in any of the three studies that have investigated this. Studies do however suggest that malaria infection in pregnancy increases the risk of a baby weighing less than 2500g at birth.

Can taking mefloquine in pregnancy cause stillbirth?

No increased risk of stillbirth was seen in four out of the five studies of pregnant women taking mefloquine that have investigated this. Although one study did suggest a possible increased risk, this study included many women with malaria which is itself known to increase the risk 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 mefloquine has been linked to permanent neurological and psychiatric changes in some non-pregnant individuals, some people have questioned whether mefloquine might 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. Two studies have each 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 children not exposed in the womb. There is currently no known link between taking mefloquine in pregnancy and learning or behavioural problems such as attention deficit hyperactivity disorder (ADHD) or autism spectrum disorder in the child, although to date, no scientific studies have specifically investigated a link with these problems.

There are many aspects of learning and behaviour that have not yet been studied in relation to mefloquine exposure in the womb, and much more research into this subject is therefore required.

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

Feedback request 

WE NEED YOUR HELP! Do you have 3 minutes to complete a short, quick and simple 12 question user feedback form about our bumps information leaflets? To have your say on how we can improve our website and the information we provide please visit

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.

My bump’s record

Create your own ‘My bump’s record’.

Provide information about your pregnancy to help women in the future.

Login to my bumps

Join my bumps