Smoking and pregnancy

Second-hand smoke exposure leads to premature birth. Learn more about how smoking can impact unborn babies.

Exposure to smoke during pregnancy harms a baby

Exposure to tobacco smoke before, during or after pregnancy can harm your baby. This includes smoke that any pregnant mother inhales when someone else is smoking around her.

Some of the effects of smoking on your baby are an increased risk of being born prematurely (too early) and with low birthweight. Babies exposed to tobacco smoke are also more likely to have lung problems and get infections.

Smoking by parents can cause:

  • sudden infant death syndrome (SIDS)
  • stillbirth
  • a rare form of liver cancer in babies.

Smoking by either parent can cause harm to their baby. To keep the mother and baby safe, no-one should smoke near a pregnant woman or a baby.

Smoking causes babies to be born too early

Smoking during pregnancy increases the chance of a premature birth. This means your baby is more likely to be born before week 37 of pregnancy, compared to the average of 40 weeks.

In general, babies born early are at higher risk of many health problems. These include: 

  • hearing and vision problems
  • infections
  • breathing and heart problems.

If born too early, your baby may need to spend the first weeks of life in intensive care to receive oxygen and warmth.

Smoking causes pregnancy complications, which are problems during pregnancy that put the mother and baby at risk. These include:

  • disruption to the placenta – where the placenta covers the opening of the womb making a vaginal birth impossible 
  • early breaking of waters – preterm premature rupture of membranes.

Both conditions can lead to premature birth, as well as more serious outcomes, such as loss of the baby.

Find out more about pregnancy complications and support.

Smoking by parents damages the baby’s lungs

Smoking by a pregnant mother causes damage to the baby’s lungs. Smoking by a partner or other people around the pregnant mother can also damage the lungs of the developing baby.

Lungs are designed to deliver oxygen to red blood cells, which then transport the oxygen to all parts of the body. Lungs also remove carbon dioxide from the blood to be breathed out. A baby’s lungs develop during pregnancy and grow larger during childhood. If their lungs do not develop properly, this may lead to lung problems in childhood and later life.  

The lungs of a new born baby whose mother is exposed to tobacco smoke do not work as well as the lungs of babies of non-smokers. They have reduced lung function.

When a pregnant woman breathes in smoke, toxic chemicals from that smoke move into her blood, then into the growing baby. Some of these chemicals may affect the lungs in the baby.

Scientists have discovered that nicotine from cigarettes damages the lungs of babies during pregnancy. Other toxic chemicals from cigarette smoke may also damage the baby’s lungs. 

How does tobacco smoke harm your baby?

Smoke from cigarettes carries over 7,000 different chemicals. Many of these are toxic to humans, such as carbon monoxide. When you breathe in smoke, these chemicals fill your lungs and move into your blood. In your blood they circulate to all parts of your body.

Chemicals from smoke can cause damage before, during and after pregnancy. If a pregnant woman smokes or inhales second-hand smoke, these chemicals can affect the developing baby.

Smoking before pregnancy

Men who smoke are more likely to have DNA damage in their sperm. This may affect their fertility and the health of their baby.

Nicotine and other toxic chemicals in smoke can change hormone levels in women. These chemicals can decrease levels of the female sex hormones called oestrogen and progesterone.

Inhaling second-hand smoke during pregnancy

During pregnancy, the embryo goes through rapid growth and many changes. Developing babies are strongly affected by the presence of toxic chemicals that harm their growth.

During pregnancy, second-hand smoke from the pregnant woman’s partner can also harm the baby. In the womb, the developing baby is exposed to chemicals from smoke that travel in the mother’s blood. Cigarette smoke leads to hormonal changes, inflammation and nutrition problems that may affect how the baby develops.

These chemicals can damage your baby’s DNA. They can also restrict blood flow in the placenta, which is needed to deliver oxygen and nutrients to your baby. When carbon monoxide from smoke gets into the bloodstream, it removes oxygen from its place inside red blood cells. Less oxygen then gets to the baby's developing body and brain, where it is needed.

Smoking near a baby

After a baby is born, they can be exposed to second-hand smoke from anyone who is close by. No-one should smoke anywhere in a house with a baby. Second-hand smoke exposure by a baby can cause SIDS – the sudden death of the child.  

You can quit smoking

Smoking by parents puts their babies at risk. Quitting smoking can reduce the risk of having a premature baby.

The best way to protect your baby is to stop smoking before pregnancy. No-one should smoke near a pregnant woman or baby.

Follow the safe sleeping guidelines to protect your baby from SIDS and keep them safe.  

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