(Date: August 2013. Version: 1)

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?

Naproxen is a ‘non-steroidal anti-inflammatory drug’ (NSAID) used to treat period pain or inflammation in rheumatism, arthritis and gout.

Is it safe to take naproxen in pregnancy?

Use of naproxen after 30 weeks of pregnancy is not advised. For some women with certain illnesses, naproxen may be prescribed before 30 weeks of pregnancy. For most women, paracetamol is usually recommended to control pain during pregnancy. If paracetamol does not control your pain, it is important that you ask your doctor for advice before taking any NSAID in pregnancy. Your doctor is the best person to help you decide what is right for you and your baby.

This leaflet summarises the scientific studies relating to the effects of naproxen on a baby in the womb. It is advisable to consider this information before taking naproxen if you are pregnant.

What if I have already taken naproxen during pregnancy?

There is no strong scientific proof that taking naproxen before week 30 of pregnancy will harm a baby in the womb. However, if you have taken or are taking 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.

If you have taken naproxen after week 30 of pregnancy it is important that you let your doctor or midwife know straight away as your baby’s wellbeing in the womb will need to be assessed. 

Can taking naproxen in pregnancy cause miscarriage?

It is unclear whether taking naproxen in early pregnancy increases the chance of having a miscarriage as there are no studies that have specifically examined this.

Some studies of women who took any type of NSAID during pregnancy (not just naproxen) suggested that these women are more likely to have a miscarriage than women who did not. However, women who take NSAIDS in pregnancy are more likely to have certain illnesses, such as rheumatoid arthritis, which are themselves thought to increase the chance of having a miscarriage. More research is needed to understand whether the increased risk of miscarriage reported in the above studies is due to the NSAIDs, the illnesses that women may need to take NSAIDs for in pregnancy, or a combination of both factors. As naproxen was not studied separately from other NSAIDs, we do not know how this information relates to women specifically taking naproxen.

Can taking naproxen 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 that taking naproxen during early pregnancy causes birth defects.

Most studies show that women who took naproxen during the first three months of pregnancy are no more likely to have a baby with a birth defect than women who didn’t. A small number of studies have suggested possible links between taking naproxen in early pregnancy and specific birth defects. In some cases, other studies of the same birth defect have shown no link. In summary, these studies (detailed below) do not provide enough evidence to prove that naproxen causes any type of birth defects: 

• One study suggested that naproxen use in pregnancy may increase the likelihood of having a baby with a heart defect, but four further studies did not find this.

• Three studies indicated that babies born to women who took naproxen in pregnancy were more likely to have cleft lip and/or palate, but this was not found in another two studies.

• Single studies have suggested a link between naproxen use in early pregnancy and various different birth defects including spina bifida (a defect of the spine), polydactyly (extra fingers or toes), limb reduction defects (where the limbs are shortened or missing) or hypospadias (where the opening on the penis is on the underside rather than at the tip). However, no other studies have investigated any possible link between naproxen use in pregnancy and these birth defects and it is therefore not possible to say that there is a link based on only one study.

Taken together, the results of these studies do not provide firm evidence to link taking naproxen during early pregnancy with any of the defects listed above.

What problems can taking naproxen after 30 weeks of pregnancy cause in my baby?

Premature closure of the ductus arteriosus
Before birth, a blood vessel in the baby called the ductus arteriosus needs to stay open to supply the baby in the womb with nutrients and oxygen from the mother. The ductus arteriosus closes just after birth to allow the baby’s blood to flow through its lungs once it starts breathing.  “premature closure of the ductus arteriosus” is the medical term used to describe this blood vessel closing before it is supposed to.

Taking naproxen or another NSAID after 30 weeks of pregnancy can cause the ductus arteriosus to close while the baby is still in the womb, and the baby may then need to be delivered early. It is important to contact your doctor or midwife straight away if you have taken a NSAID after 30 weeks of pregnancy, especially if you have taken several doses or more than the recommended dose.

Persistent pulmonary hypertension of the newborn (PPHN)
PPHN or ‘persistent pulmonary hypertension of the newborn’ occurs when a newborn baby’s lungs do not adapt to breathing outside the womb. It is thought to be linked, in some cases, to premature closure of the ductus arteriosus (see above) and has also been linked to taking NSAIDs, including naproxen, around the time of delivery. PPHN only affects around 1 or 2 out of every 1,000 newborn babies in the general population, but is important as it can be serious.

Oligohydramnios (reduced fluid around the baby)
Use of NSAIDs after 30 weeks of pregnancy may cause oligohydramnios, (where there is too little amniotic fluid in the sac around the baby). Oligohydramnios can result in:

• Poor development of the baby’s lungs (because inhaling amniotic fluid while in the womb helps to expand and develop the lungs).

• The baby’s bladder being under-developed (because urine expands and develops the bladder).

• The baby’s skull and leg bones being misshapen and the baby having ‘flattened’ facial features (as a result of there not being enough amniotic fluid to ‘cushion’ the baby in the womb).

• Compression (squashing) of the umbilical cord, which may result in reduced blood flow from the mother to the baby in the womb.

If you have taken naproxen after 30 weeks of pregnancy your doctor may wish to check your amniotic fluid levels by ultrasound scan.

Wherever possible, use of naproxen during the third trimester of pregnancy should be avoided. Please discuss any concerns that you may have with your doctor.

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

A single study showed that women who had taken naproxen during pregnancy were no more likely to give birth early (before 37 weeks of pregnancy) or to have a low birth weight baby (<2500g) than pregnant women who had not taken naproxen. However, because these results are from just one study, more data needs to be collected on this subject.

Can taking naproxen 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.

There is no known link between taking naproxen in pregnancy and learning or behavioural problems such as attention deficit hyperactivity disorder (ADHD) or autism spectrum disorder in the child. 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 naproxen before 30 weeks of pregnancy would not normally require extra monitoring of your baby.

If you have taken naproxen after 30 weeks of pregnancy you may need extra scans or monitoring of your baby. 

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

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