When you smoke, or breathe in someone else's smoke, CO gets into your bloodstream and lessens the amount of oxygen that gets to your baby, which can affect their growth and development.
Babies need oxygen to grow and develop and it is delivered to them through the placenta. If you smoke, the carbon monoxide and other harmful gases replace oxygen in the baby's bloodstream, lessening the amount of oxygen they receive. This slows its growth and development, and increases the risk of miscarriage, stillbirth and sudden infant death.
When you stop smoking, it takes just 24 hours for the harmful CO to clear from your bloodstream, so your baby will start getting more oxygen via the placenta very quickly if you quit during pregnancy.
If you are or were a smoker, your midwife or stop smoking advisor can give you a carbon monoxide (CO) breath test to see how clear your lungs are. The test is simple and easy and 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:
ℹLast reviewed on April 1st, 2015. Next review date April 1st, 2018.