High dose fluconazole (400-800mg per day)

(Date: May 2016. Version: 2.2)

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?

Fluconazole (Diflucan®) is sometimes used at high doses (400-800mg per day) to treat very serious, often life-threatening fungal infections that are most likely to occur in individuals with weakened immune systems (e.g. due to HIV infection or chemotherapy). It is sometimes necessary for high dose treatment to be continued for a long period of time. The information in this leaflet relates to use of HIGH DOSE FLUCONAZOLE ONLY.

A much LOWER DOSE OF FLUCONAZOLE (usually a single 150mg tablet) is used for the treatment of vaginal thrush. Please see the bump leaflet relating to fluconazole treatment of thrush if you have taken or have been prescribed the 150mg dose.

Is it safe to take high dose fluconazole in pregnancy?

Treatment with high doses of fluconazole (400-800mg per day) for extended periods in the first 12 weeks of pregnancy may cause birth defects (see below). However, for pregnant women with serious and/or life threatening fungal infections, treatment with high dose fluconazole may be the best option for both mother and baby.

Your doctor is the best person to help you decide what is right for you and your baby.

What if I have already taken high dose fluconazole during pregnancy?

If you are pregnant and have taken high dose fluconazole (400-800mg per day) it is important that you let your doctor know. This leaflet summarises the available scientific information about the effects of high dose fluconazole on a baby in the womb. This information is intended to help you to understand the risks to your baby and to make an informed decision, together with your doctor, regarding your pregnancy.

Can using high dose fluconazole 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.

Similar facial and bone abnormalities have been reported in five babies born to four women who were treated with high dose fluconazole in the first trimester of pregnancy. However, another mother who took high dose fluconazole in the first trimester gave birth to a healthy baby with no birth defects.  

High dose fluconazole treatment in pregnancy is very uncommon and not enough information has been collected to predict the chance of a pregnant woman who has taken high dose fluconazole having a baby with birth defects. We also do not know whether a single treatment with a high dose of fluconazole during early pregnancy increases the chance of birth defects in the baby.

It is important to seek advice from your obstetrician before making any decisions based on the information in this leaflet. The risk of a medicine causing birth defects changes with each week of pregnancy (even in the first trimester). The risk of your baby being affected by high dose fluconazole may therefore be much lower than you might think from reading the information above.

Can taking high dose fluconazole in pregnancy cause miscarriage, stillbirth, preterm birth, or my baby to be small at birth (low birth weight)?

No studies have looked at the risk of miscarriage, stillbirth, preterm birth, or low birth weight in women who took high doses of fluconazole during pregnancy.

Can taking high dose fluconazole 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.

No scientific studies have investigated whether there may be a link between taking high dose fluconazole in pregnancy and learning or behavioural problems (such as ADHD or autism spectrum disorder) in the child later on in life.

Will my baby need extra monitoring during pregnancy?

Most women will be offered a scan at around 20 weeks of pregnancy to look for birth defects as part of their routine antenatal care.

Women who have been treated with high dose fluconazole during the first 12 weeks of pregnancy may be offered the option of having more detailed anomaly scans to look for birth defects from as early as around 12 weeks of pregnancy. It is, however, harder to see birth defects at this stage of pregnancy, which is why the main scan for birth defects is generally offered at around 20 weeks. It is important to understand that scans are not able to detect all birth defects and cannot rule out that a baby will have problems with learning.

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

We would not expect any increased risk to your baby if the father took fluconazole before or at around the time you became pregnant.

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 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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