Date: August 2018, Version 1.0

Smoking during pregnancy

There is strong scientific evidence that smoking during pregnancy increases the likelihood of miscarriage, certain birth defects, premature birth, and poor growth of the baby in the womb, which has been linked to certain health problems later in life.

Pregnant women and women trying to conceive should ideally stop smoking. While it is better to have given up smoking before pregnancy, research shows that stopping smoking or cutting down significantly in early pregnancy can reduce the risk of the baby having some of the health problems linked to smoking. If you need help to stop smoking you should speak to your doctor or midwife.

Can smoking in 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 exposure to certain substances is known to cause birth defects.

There is strong scientific evidence from a large number of studies that smoking during early pregnancy increases the chance of a baby being born with cleft lip and/or palate.

Some studies have also suggested that smoking during pregnancy might be linked to a number of other birth defects in the baby, including:

• Craniosynostosis (an abnormally shaped skull caused by the bones fusing too early)
• Gastroschisis (where part of the bowel protrudes through a hole next to the tummy button)
• Defects of the urinary tract (including defects of the kidneys and bladder)
• Heart defects 
• Congenital diaphragmatic hernia (a hole in the sheet of muscle below the lungs that can cause the abdominal organs to move upwards, preventing the lungs from developing properly)
• Talipes (where one or both of the baby’s feet are turned inwards and downwards)

Can smoking in pregnancy cause miscarriage?

A number of studies have linked smoking during pregnancy with miscarriage. Studies have also linked smoking before and during pregnancy to having an ectopic pregnancy (where the embryo implants in the fallopian tube instead of in the womb). This can be life-threatening for the mother and always results in loss of the baby.

Can smoking in pregnancy cause premature delivery and low birth weight?

Smoking during pregnancy is linked to premature birth (before 37 weeks of pregnancy) and low birth weight (less than 2,500g). Smoking during pregnancy appears to reduce the rate at which a baby grows in the womb, possibly by reducing the blood and oxygen supply to the baby through effects on the placenta. Studies have shown that the more a woman smokes during pregnancy the more likely she is to have a premature birth and/or a low birth weight baby. However, it has been shown that pregnant women who give up smoking in the very early weeks of pregnancy are no more likely to have a low birth weight baby than women who don't smoke in pregnancy.

Can smoking in pregnancy cause stillbirth?

Several studies have shown that smoking during pregnancy increases the chance of stillbirth. It has been suggested that women who smoke during pregnancy may be about twice as likely to have a stillbirth as women who do not smoke. This is thought to be at least partly explained by the fact that smoking during pregnancy is linked to problems with the placenta, including placental abruption (where the placenta detaches from the womb before the baby is born), which can be life-threatening for both mother and baby.

Can smoking in pregnancy cause other health problems in the child?

Sudden infant death syndrome (SIDS)
Smoking during and after pregnancy increases the risk of SIDS (“cot death”). Studies have shown that babies whose mothers smoked were about three times more likely to die of SIDS than babies of non-smoking mothers. However, one study has shown that babies born to mothers who gave up smoking during first 12 weeks of pregnancy were not at increased risk of SIDS.

Childhood illness
Babies and children whose mothers smoked during and after pregnancy have been shown to be more likely to suffer from colic, obesity, ear infections and respiratory illnesses (e.g. chest infections).

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.

Several studies have now shown that children whose mothers smoked during pregnancy are more likely to have problems with thinking, learning and behaviour, than children whose mothers did not smoke.

However, studying whether problems with learning or behaviour are caused by exposure to a particular substance in the womb can be difficult. Many of the children in these studies were also exposed to cigarette smoke after birth, meaning that it is not possible to confirm that these problems were caused specifically by smoking in pregnancy. More research into the potential effects of smoking during pregnancy on the learning and development of the child is therefore required.

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.

Women who smoke heavily during pregnancy may be offered extra monitoring of their baby’s growth.

Are there any risks to my baby if the father smokes?

Most of the problems described above that have been linked to smoking in pregnant women have also been linked to ‘passive’ smoking during pregnancy (breathing in second-hand smoke from the air). Ideally, a pregnant woman should avoid breathing in smoke from others, as well as not smoking herself.

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

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

How can I help to improve drug safety information for pregnant women in the future?

Our online reporting system (MyBump Portal) allows women who are currently pregnant to create a secure record of their pregnancy, collected through a series of questionnaires. You will be asked to enter information about your health, whether or not you take any medicines, your pregnancy outcome and your child's development. You can update your details at any time during pregnancy or afterwards. This information will help us better understand how medicines affect the health of pregnant women and their babies. Please visit the MyBump Portal to register.

General information
Sadly, miscarriage and birth defects can occur in any pregnancy.

Miscarriage occurs in about 1 in every 5 pregnancies, and 1 in every 40 babies are born with a birth defect. This is called the ‘background risk’ and happens whether medication is taken or not.

Most medicines cross the placenta and reach the baby. For many medications this is not a problem. However, some medicines can affect a baby’s growth and development.

If you take regular medication and are planning to conceive, you should discuss whether your medicine is safe to continue with your doctor/health care team before becoming pregnant. If you have an unplanned pregnancy while taking a medicine, you should tell your doctor as soon as possible.

If a new medicine is suggested for you during pregnancy, please make sure that the person prescribing it knows that you are pregnant. If you have any concerns about a medicine, you can check with your doctor, midwife or pharmacist.

Our Bumps information leaflets provide information about the effects of medicines in pregnancy so that you can decide, together with your healthcare provider, what is best for you and your baby.