(Date: July 2010. Version: 1a)

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 is heroin?

Heroin is a recreational drug that is smoked or injected.

Is it safe to use heroin in pregnancy?

When a pregnant woman uses heroin, it enters her bloodstream and crosses the placenta to the baby. Heroin in the baby’s bloodstream reaches the baby’s heart, brain, and other organs, and has been shown to affect the breathing movements and heart rate of a baby in the womb. Taking too much heroin, or heroin that contains other drugs or substances, can result in poisoning or even death of mother and baby.

The long term effects of heroin use in pregnancy on the baby are still unclear. Heroin should not be used in pregnancy or by women who are trying to become pregnant.

What if I have already used heroin during pregnancy?

If you are pregnant and use heroin, you should let your doctor or midwife know. They will be able to get you help and support to safely stop using heroin. You should not stop or reduce the amount of heroin you take without a doctor’s guidance, as this could cause withdrawal symptoms that may be very dangerous to both you and your baby.

Can using heroin during pregnancy cause 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 substances are known to cause birth defects.

Although no link between heroin use in pregnancy and birth defects in the baby is currently known about, it is very difficult to accurately study the effects of illicit drugs like heroin on a developing baby. It is therefore currently not possible to say for certain that heroin does not cause birth defects.

Can using heroin during pregnancy cause miscarriage, stillbirth, or premature delivery?

No known links between heroin use in pregnancy and miscarriage, stillbirth, or premature delivery (before 37 weeks of pregnancy) have been identified. However, studying the effects of heroin use in pregnancy is complex and as a result, the scientific research that has been done cannot rule out links between these pregnancy outcomes and heroin use.

Sudden heroin withdrawal can cause miscarriage, stillbirth and premature delivery. This is one of the reasons why pregnant women who use heroin should not stop or reduce the dose that they use without medical support.

Can using heroin in pregnancy cause low birth weight?

Some studies have shown that use of heroin in pregnancy is linked to reduced growth of the baby in the womb and to having a low birth weight baby. Babies with a low birth weight (<2500g) appear to have a higher risk of health problems such has heart disease later on in life. However, because women who use heroin in pregnancy may be more likely to use other drugs, to smoke, to drink alcohol, to have poor nutrition, and to have health conditions (all of which may affect a baby’s growth in the womb), it is difficult to say for sure that heroin directly affects birth weight.

Can using heroin in pregnancy cause other health problems in the child?

Withdrawal symptoms at birth (neonatal withdrawal)
Withdrawal symptoms are thought to occur as a result of the newborn baby’s body having to adapt to no longer getting addictive substances through the placenta.

Studies have shown that up to four out of every five babies exposed to heroin while in the womb will experience withdrawal symptoms at birth. These symptoms can range from mild to life-threatening. Therefore, if you have used heroin in the weeks before delivery, your baby is likely to require close monitoring and/or supportive treatment for a few days after birth. It is essential that you tell your doctor or midwife if you have been using heroin during pregnancy so that they can arrange for your baby to be born at a unit which can monitor your baby and so that any necessary treatment for withdrawal symptoms can be started as soon as possible.  

Sudden infant death syndrome (SIDS)
Studies have shown that babies whose mothers used heroin in pregnancy were up to ten times more likely to die of SIDS (“cot death”) than babies of mothers who did not use drugs. However, it is unclear whether this is directly related to heroin use in pregnancy, or whether other lifestyle factors of heroin users either during pregnancy, or whilst caring for a baby may contribute to this increased risk.

Learning or behavioural problems
A baby’s brain continues to develop right up until the end of pregnancy. It is therefore possible that exposure to certain substances at any stage of pregnancy could have a lasting effect on a child’s learning or behaviour.

Heroin acts on the brain directly and affects thinking and emotion.  There are therefore concerns that using heroin during pregnancy could have lasting damaging effects on an unborn baby’s developing brain.

Some studies of children whose mothers used heroin during pregnancy have shown that these children are more likely to have problems with thinking, learning, and behaviour than children whose mothers did not use heroin. However, other studies have not agreed with this. It is still not known whether the differences in learning, intelligence and behaviour seen in some of these studies were caused by heroin, or by other factors during pregnancy such as the mother’s health or alcohol and cigarette use. Additionally, many of the mothers of the children in these studies continued to use illicit drugs whilst caring for their babies/children, and this may have also affected the child’s long-term development.

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.

If you have used heroin during pregnancy it is best for you and your baby that you tell your doctor or midwife as soon as possible. They will then be able to make sure that you and your baby receive extra monitoring or support if necessary.

Are there any risks to my baby if the father uses heroin?

No studies have specifically investigated whether heroin used by the father can harm the baby through affects on the sperm, however most experts agree that this is very unlikely. More research on the effects of drug and medicine use in men around the time of conception is needed.

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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