Tommy's PregnancyHub

Carbon monoxide testing is not just for pregnant women who smoke

Public Health England suggest that all pregnant women should be tested for carbon monoxide. Our midwife Sophie explains why this testing is important.

Duncan Selbie, the Chief Executive of Public Health England has caused controversy after suggesting that all pregnant women should be tested for carbon monoxide (CO) at their booking appointment.

Selbie put forward the recommendation in a letter to NHS colleagues advising them on how to reduce the number of smokers in the UK.

While smoking in pregnancy is known to increase the risk of miscarriage, premature birth and stillbirth, several mothers have expressed outrage online at the idea of compulsory carbon monoxide testing.

Several mums expressed their upset on Mumsnet

One Mumsnet user felt the test 'treated pregnant women like children' and shows that they are not trusted to tell their midwives the truth about whether or not they smoke.

One user commented: 'I think this is outrageous – why aren’t pregnant women being trusted to tell the truth?' Another added: 'Really terrible idea. Pregnant women are not just baby incubators.'

Our midwife Sophie explains why carbon monoxide testing in pregnancy is important:

'We understand that the test may feel like there is a lack of trust between you and your midwife, but there are really good reasons for having the carbon monoxide test, whether you are a smoker or not. 

Many hospitals already do carbon monoxide testing at booking appointments for all women. For safety, both smoking and non-smoking women are tested. Aside from identifying pregnant smokers and offering them help to quit, it can often prompt lifesaving checks to home boilers. A small percentage of non-smoking women, have high carbon monoxide readings due to faulty boilers leaking the potentially deadly gas.

The test takes only seconds and can give the midwife and pregnant woman key information that allows them to reduce their exposure to carbon monoxide and have a healthier pregnancy. Women should always feel able to speak to their midwife about anything that might be affecting their health and no midwife will ever judge a pregnant mother seeking help to quit smoking.'

Reasons pregnant women are tested for carbon monoxide

There are several reasons why pregnant women are tested for carbon monoxide whether or not they smoke.

  • To see if you are at risk of CO poisoning from a faulty appliance and you should call the Health and Safety Executive gas safety line.
  • To show whether you’re inhaling harmful amounts of secondhand smoke.
  • If you do smoke, then your midwife can discuss the dangerous effects of carbon monoxide on you and your baby with you, and give you help and advice on how to quit.

 How the carbon monoxide breath test works

  • You blow into a hand-held machine, called a CO monitor, which measures the level of CO in your body.
  • Some machines can also work out how much CO is getting to your baby.
  • The more CO you have inhaled, the higher your CO reading will be.
  • In other words, the more smoke you have inhaled, the more CO you will have in your body.

If you see the results of the CO test, the reading is measured in COppm, which means the number of CO molecules in one million parts of air. Women with a CO test reading of 3ppm or higher may be referred to stop smoking services. 

When you stop smoking, your CO readings will fall showing that you and your baby are becoming free from this poisonous gas.

Factors like faulty heating in the home and secondhand smoke are why testing all pregnant women, non smokers as too, for carbon monoxide is so important.

Find out what questions you'll be asked at the booking appointment here.

Find our more about carbon monoxide testing here.