(Date of issue: June 2011. 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.
Smoking during pregnancy
Cigarette smoke contains nicotine and over 4,000 other chemicals, many of which are known to be poisonous to humans. When a pregnant woman smokes these chemicals enter her bloodstream and cross the placenta to the baby. Studies have shown that nicotine accumulates in the amniotic fluid around the baby, in the baby’s blood and reaches the baby’s vital organs.
There is strong scientific evidence that smoking during pregnancy increases the risk of miscarriage, certain birth defects, premature birth, and poor growth of the baby in the womb, which has been linked to health problems later on in life.
What if I have already been smoking during pregnancy?
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 (a split in the lip and/or the roof of the mouth).
Some studies have also suggested that smoking during pregnancy might be linked to a number of other birth defects in the baby (listed below). However, until further research is carried out we cannot say for sure that smoking causes any of these birth defects.
• craniosynostosis (an abnormally shaped skull caused by the baby’s skull bones fusing too soon)
• gastroschisis (where part of the baby’s bowel protrudes outside of the baby’s body 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 baby’s diaphragm - which is the muscular sheet that separates the lungs and the abdomen or tummy. As a result, the baby’s liver and other abdominal organs are pushed up into the chest squashing the baby’s lungs which can then not develop properly)
• talipes (“club foot” - 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. One study showed that women who smoked during pregnancy were about twice as likely to have a miscarriage as women who didn’t smoke.
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 2500g). 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 affects 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 didn’t smoke in pregnancy.
Can smoking in pregnancy cause stillbirth?
Several studies have shown that smoking during pregnancy increases the risk 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.
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.
Smoking during pregnancy would not normally require extra monitoring of your baby, although if you have smoked heavily during pregnancy your baby’s growth may be monitored more closely.
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 smoke herself.
Are E-cigarettes safe to use in pregnancy?
E-cigarettes contain nicotine as well as a number of other chemicals. No studies have investigated pregnancy outcomes in women who used E-cigarettes during pregnancy. The effects of E-cigarette use on a developing baby are therefore unknown.
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.
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.