(Date: August 2015. Version: 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?

Omeprazole (Losec®) is a medicine called a proton pump inhibitor (PPI). PPIs reduce the production of stomach acid. PPIs are used to treat indigestion, gastro-oesophageal reflux and stomach ulcers, all of which are more common in pregnancy as a result of the normal changes that occur as pregnancy progresses. Omeprazole is the only PPI that is licensed in the UK for use in pregnancy. Much less is known about how the other four PPIs (lansoprazole, esomeprazole, pantoprazole and rabeprazole) that are licensed in the UK might affect an unborn baby and their use in pregnancy is therefore generally not advised.

Is it safe to take omeprazole in pregnancy?

Omeprazole is widely used in pregnant women. It is not known to be harmful to an unborn baby, but as is the case for nearly all medicines, the possible effects that exposure in the womb may have on a child’s longer term health have not been studied. When deciding whether or not to take omeprazole during pregnancy it is therefore important to weigh up the benefits of its use against the known or possible risks, some of which will depend on how many weeks pregnant you are. You might also be able to reduce some of your symptoms by eating smaller meals more frequently, avoiding fatty and spicy foods, and raising the head of your bed.

This leaflet summarises the scientific studies relating to the effects of omeprazole on a baby in the womb. It is advisable to consider this information before taking omeprazole if you are pregnant. For some women treatment with omeprazole in pregnancy may be necessary.

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

What if I have already taken omeprazole during pregnancy?

If you have taken any medicines it is always a good idea to let your doctor know that you are pregnant so that you can decide together whether you still need the medicines that you are on and to make sure that you are taking the lowest dose that works.

Can taking omeprazole 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.

None of the eight studies, that together included a total of more than 4,000 pregnant women, have shown that babies whose mothers took omeprazole in the first trimester of pregnancy are any more likely to have a birth defect than babies of healthy women who did not take omeprazole.

A small number of studies have investigated whether some specific birth defects are more likely to occur in babies exposed to omeprazole in the womb. The studies found no evidence that omeprazole use in early pregnancy increases the chance of the baby having a heart defect, hypospadias (where the opening of the penis is on the underside rather than the tip), or cleft lip and/or palate.

Can taking omeprazole in pregnancy cause miscarriage?

Two small studies provided no evidence of an increased risk of miscarriage in pregnant women taking omeprazole. Although this is reassuring, many more pregnant women taking omeprazole need to be studied to confirm this finding.

Can taking omeprazole in pregnancy cause stillbirth?

A single small study provided no evidence that omeprazole use in pregnancy increases the risk of stillbirth. However, stillbirth rates need to be studied in more pregnant women taking omeprazole to confirm this finding.

Can taking omeprazole in pregnancy cause preterm birth, or my baby to be small at birth (low birth weight)?

There is no proof that omeprazole use in pregnancy increases the chance of preterm birth or of the baby having a low birth weight. However, the number of pregnancies studied with respect to these outcomes is quite low, and these findings (summarised below) therefore require further confirmation.

Four studies which included a total of 1,500 babies exposed to omeprazole in the womb showed no harmful effect on birth weight.

None of three studies of a total of 475 pregnancies during which omeprazole was taken have indicated that the risk of preterm delivery is increased.

Can taking omeprazole in pregnancy cause other health problems in the child?

Allergy and asthma
A number of studies have shown that use in pregnancy of a number of different medicines that suppress the production of stomach acid might increase the risk of allergy and asthma in the child. Studies specifically of PPIs (including omeprazole) have produced mixed results. Two studies of asthma rates did not agree; one study showed that asthma is more common in children of women who took a PPI in pregnancy, whereas the other found no increase in risk.

Single studies have each shown that exposure to PPIs in the womb may increase the risk of a child developing allergy and allergic rhinitis (inflammation of the nose that causes sneezing and a runny nose), but another study found no link between PPI use in pregnancy and allergic eczema in the child.

Further research is required to determine whether PPI use in pregnancy increases a child’s chance of developing asthma and allergies.

Learning and behavioural problems
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.

There is no known link between taking omeprazole in pregnancy and learning or behavioural problems (such as ADHD or autism spectrum disorder) in the child later on in life. There are, however, no scientific studies that have specifically investigated a link with these problems.

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. Taking omeprazole in pregnancy is not expected to cause problems that would require extra monitoring of your baby.

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

We would not expect any increased risk to your baby if the father took omeprazole before or 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  

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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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