Carbon monoxide testing in pregnancy

Patient Information Leaflet

What is Carbon Monoxide?

• Carbon Monoxide (CO) is a poisonous gas.
• You cannot smell it, see it or taste it.
• CO is absorbed into your blood stream when you breathe it in.
• CO is found in both indoor and outdoor air. Some of the causes for it are listed below.

Indoor air

• Tobacco smoke
• Second hand smoke or passive smoking of any tobacco product
• Smoke from burning charcoal
• Open fire and woodburning stove
• Smoke from burning candles and incense
• Unvented kerosene heaters
• Fumes from faulty gas appliances (gas boilers, gas cookers and heaters)

Outdoor air

• Tobacco smoke
• Second hand smoke or passive smoking of any tobacco product
• Traffic exhaust fumes
• Fumes from leaking chimneys and furnaces.

How can CO affect my baby?

• When you breath in CO, the gas is absorbed into your bloodstream and replaces some of the oxygen going into your lungs.
• This reduces the amount of oxygen going into you and your baby's body.
• This is because CO is absorbed into your bloodstream 200 times more quickly than oxygen.
• Breathing in CO is very dangerous when you are pregnant as it deprives your baby of oxygen.
• CO in your blood (and your baby's blood) can make your placenta not work as well as it should.
• This might cause your baby to move less to save energy, which can affect how your baby grows and develops.
• Breathing in CO can also increase the risk of miscarriage, stillbirth and Sudden Infant Death Syndrome (SIDS).

How can you test for Carbon Monoxide?

• During your pregnancy you will be regularly tested for CO levels in your blood using a CO monitor.
• This tests the amount of CO in your bloodstream through a simple breath test.
• The CO test results are measured in part per million (ppm), which means the number of CO molecules in one million parts of air.
• Pregnant people with a CO reading of 4ppm or higher will be referred to our Maternity Tobacco Dependency Specialist for advice.

Why 4ppm or higher?

• We refer pregnant people with a CO reading of 4 ppm or higher because carbon monoxide is absorbed quickly into the bloodstream during pregnancy.
• This means that you and your baby can be exposed to higher levels of CO more quickly.
• Whilst you can get rid of the CO in your bloodstream (for example, by breathing it out), your baby cannot.
• This means that your baby will have 10-15% higher levels of CO in their bloodstream.

Why will a referral to the Tobacco Dependency Specialist be done even if I am a non-smoker?

• The Tobacco Dependency Specialist can advise you about the possible causes of higher levels of CO in the environment (outdoor air) and exposure to second-hand tobacco smoke, faulty boilers and other causes (indoor air).
• They can also advise you about CO levels in your home, including your landlord’s legal responsibility to make sure gas appliances meet gas safety standards.
• They can also explain other possible causes of raised CO levels indoors.
• Advice and support are also available for smokers living in or visiting your property.

Where can I find out more information?

• Gas Safe Register: Carbon monoxide poisoning https://www.gassaferegister.co.uk/media/3639/gsw-carbon-monoxide-factsheet.pdf
• Domestic gas health and safety
  https://www.hse.gov.uk/gas/domestic/index.htm
• NHS: Carbon monoxide poisoning
  https://www.nhs.uk/conditions/carbon-monoxide-poisoning/

Who to contact if I am worried about Carbon Monoxide exposure?

• If you are worried about a faulty or leaking boiler or gas appliance, please contact the gas emergency line on 0800 111 999 immediately and ensure that you contact your landlord if applicable.
• If you think you or any of your household have symptoms of CO poisoning, then contact 999/111.
• If you have any questions in relation to treating tobacco dependency and CO, please contact your Midwife or the Maternity Tobacco Dependency Service.

Useful Contacts

Whittington Health Maternity Service: 020 7288 5586
Whittington Health Maternity Tobacco Dependency Service: whh-tr.maternitytds@nhs.net