What happens when a pregnant woman smokes?

Smoking in pregnancy is harmful to your baby. Quitting is one of the best things you can do to protect your baby’s health through pregnancy and beyond.

Every day a baby dies in the UK because their mother smoked in pregnancy. Most people know that smoking is bad for you, but if you're a smoker and pregnant it can harm your growing baby too. The good news is that there is lots of help available to quit.

What happens when a pregnant woman smokes a cigarette?

When you smoke your baby does too. Every cigarette contains 4,000 chemicals, which go into your lungs when you smoke. Once they've gone into your lungs, the nicotine, poisons and carbon monoxide cross the placenta to the baby.

Nicotine narrows your blood vessels, which reduces the blood flow in the placenta. Less blood means less oxygen and nutrients reach the baby and because of this they may not grow as well as expected.

Babies born to smokers tend to weigh less at birth than babies born to non-smokers.

Toxins that damage the placenta

Cigarette smoke contains toxins that can damage the placenta. This increases your risk of dangerous problems, such as placental abruption, where the placenta starts to come away from the wall of the womb.

These toxins also affect the growth and development of your baby, increasing the risk of miscarriage, prematurity, low birthweight and stillbirth.

The more cigarettes you smoke, the greater the risk. This is why it's important to get help to stop completely as soon as possible.

How can smoking during pregnancy harm my baby?

Research shows that smoking in pregnancy may harm your baby in a number of different ways. These include:

Smoking when pregnant can also affect your child as he or she grows up. Children of smokers are more likely than children of non-smokers to have a range of health and behaviour problems, including:

  • colic
  • infections in the airways
  • ear infections
  • asthma
  • ADHD (attention deficit hyperactivity disorder)
  • autism.

Smoking can damage a baby's brain development during pregnancy and children born to smokers are also more at risk of having learning difficulties and behavioural problems as they grow up.

Babies of smokers also have a higher risk of cot death.

Smoking during pregnancy also means your child is more likely to become a smoker than if you don't smoke.

While these problems can be very serious, the good news is that you can reduce the risk of them all by quitting.

Quitting smoking: did you know?

Many women give up successfully. Smoking rates recorded at delivery have fallen to their lowest recorded level nationally! 

Talking to your midwife about smoking

At your first antenatal appointment, your midwife will ask lots of questions about your lifestyle, including whether you smoke or have recently quit. You'll also be asked whether anyone in your household smokes.

It’s very important that you tell them if you smoke. Your midwife will not judge you if you are a smoker. They know how hard it is to stop and they will be very keen to help you in any way they can, and can put you in touch with experts for advice about quitting.

Find out about what help you can get to stop smoking in pregnancy


  1. Smoking in Pregnancy: Communication with Women Working Group (2015) Shared key messages
  2. Stocks, J., & Dezateux, C. 2003. The Effect of Parental smoking on Lung Function and Development During Infancy. Respirology, 8, 266-285
  3. Royal College of Physicians 1992. Smoking and the young.  Fleming P, Blair PS. Sudden Infant Death Syndrome and parental smoking. Early Human Development. 2007;83:721-725 RCP 2010, Passive Smoking and Children, Soc Sci Med. 2005 Mar;60(5):1071-85, https://www.rcplondon.ac.uk/sites/default/files/documents/passive-smoking-and-children.pdf
  4. Petrou et all 2005, The association between smoking during pregnancy and hospital inpatient costs in childhood, http://www.ncbi.nlm.nih.gov/pubmed/15589675
  5. NHS Choices [accessed 28/04/2016] Smoking wand pregnancy,http://www.nhs.uk/conditions/pregnancy-and-baby/pages/smoking-pregnant.aspx
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    Last reviewed on April 1st, 2014. Next review date April 1st, 2017.

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