Carbon monoxide (CO) is a colourless, odourless and tasteless poisonous gas which can kill people. It is present in exhaust fumes, faulty gas appliances, coal/wood fires, oil burning appliances and cigarette smoke. It is especially dangerous during pregnancy because it deprives the baby of oxygen, slows its growth and development, and increases the risk of miscarriage, stillbirth and sudden infant death. This is why it is important to offer and encourage pregnant women to have the CO screening.