H2 receptor antagonists

(Date: June 2020. 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 are H2 receptor antagonists (H2RAs)?

H2 receptor antagonists (H2RAs) reduce the production of stomach acid and are used to treat indigestion, acid reflux, and ulcers in the digestive system. They include medicines such as ranitidine (Gavilast, Zantac), cimetidine (Tagamet®), famotidine (PepcidTwo), and nizatidine. Ranitidine is commonly given before an anaesthetic to reduce the risk of stomach acid going into the lungs.

Note: Ranitidine is currently unavailable in the UK due to concerns that it may contain an impurity. Your doctor or pharmacist will be able to advise you on other medicines for treating indigestion and reflux during pregnancy (for example omeprazole).

Is it safe to take an H2RA in pregnancy?

When deciding whether to use an H2RA during pregnancy it is important to weigh up the potential benefits to your health and wellbeing against any possible risks to you or your baby. Your doctor or specialist will be able to help you make decisions about your treatment.

What if I have already taken an H2RA during pregnancy?

If you are taking any medicines while pregnant you can discuss this with your doctor. You can then decide together whether ongoing treatment is appropriate and, if so, your doctor will ensure that you are taking the most effective dose.

Can taking an H2RA in pregnancy cause birth defects in the baby?

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 are no concerns that H2RAs cause birth defects in the baby. This has been confirmed by studies of over 2,000 women.

Can taking an H2RA in pregnancy cause miscarriage or stillbirth?

H2RAs do not appear to be linked to miscarriage. Large studies of pregnant women taking any H2RA, and smaller studies of women taking ranitidine, do not show that their use causes stillbirth.

Can taking an H2RA in pregnancy cause preterm birth or my baby to be small at birth (low birth weight)?

Taking H2RAs in pregnancy does not increase the chance of having a preterm birth (before 37 weeks) or of having a baby with a low birth weight (<2,500g).

Can taking an H2RA in pregnancy cause learning and 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.

Evidence is limited; however a study has reassuringly shown that children who had been exposed in the womb to any H2RA met their developmental milestones at the same time as children who had not been exposed in the womb to H2RAs. Ongoing research into the learning and behaviour of children exposed in the womb to H2RAs is ideally required.

Will my baby need extra monitoring?

All women are offered a scan at around 20 weeks of pregnancy to look for birth defects and to check the baby’s growth as part of routing antenatal care. Taking an H2RA in pregnancy does not require any extra scans or monitoring of your baby.

Are there any risks to my baby if the father has taken an H2RA?

We would not expect any increased risk to your baby if the father took an H2RA 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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