Effects of carbon monoxide

Carbon monoxide (CO) is a poisonous gas. It can come from unsafe gas appliances, burning coal, wood, petrol and oil. It also forms when cigarettes (including roll-ups) burn.

Your baby receives all the oxygen, nutrients and antibodies they need from your blood supply. When you smoke (or if you breathe in other people’s smoke) the carbon monoxide, and other damaging chemicals, restricts the oxygen your baby gets. This affects your baby’s growth and development and causes your baby’s heart to beat harder every time you smoke.

Smoking also increases the risk of:

Stopping smoking will help you and your baby immediately. When you stop smoking, it only takes 24 hours for the harmful CO and other chemicals to clear from your bloodstream. Your baby will start getting more oxygen through the placenta very quickly and you will reduce the risks of complications in pregnancy and birth. Find out how you can get help to stop smoking.

Testing your carbon monoxide levels

Your midwife should carry out a carbon monoxide test as part of your routine antenatal care. This simple test will show how much of this gas you and your baby have been exposed to.

Watch our short animation on the effect of smoking in pregnancy

NHS Choices. Stop smoking in pregnancy. https://www.nhs.uk/conditions/pregnancy-and-baby/smoking-pregnant/ (Page last reviewed: 07/11/2019). Next review due: 07/11/2022)

Action on Smoking and Health (ASH) (2014) Stopping smoking. https://ash.org.uk/wp-content/uploads/2019/10/StoppingSmoking-BenefitsAndAids.pdf 

Review dates
Reviewed: 23 January 2020
Next review: 23 January 2023

This content is currently being reviewed by our team. Updated information will be coming soon.