NICE guidance - stopping smoking in pregnancy

Last edited 12/2021 and last reviewed 12/2021

Smoking cessation advice during pregnancy should be undertaken by mdwives (at first maternity booking and subsequent appointments)

What action should the midwife take?

• provide routine carbon monoxide testing at all antenatal appointments to assess the pregnant woman's exposure to tobacco smoke
  • explain that the CO test will allow her to see a physical measure of her smoking and her exposure to other people's smoking
  • ask her if she or anyone else in her household smokes. To help interpret the CO reading, establish whether she is a light or infrequent smoker
  • other factors to consider include the time since she last smoked and the number of cigarettes smoked (and when) on the test day. (Note: CO levels fall overnight so morning readings may give low results.)
    
    
• provide an opt-out referral to receive stop-smoking support for all pregnant women who:
  
  
  • say they smoke or have stopped smoking in the past 2 weeks or
    
    
  • have a carbon monoxide reading of 4 parts per million (ppm) or above or
    
    
  • have previously been provided with an opt-out referral but have not yet engaged with stop-smoking support

Explain to the woman:

• that it is normal practice to refer all pregnant women who smoke or have recently quit

• that the carbon monoxide test will allow her to see a physical measure of her smoking and exposure to other people's smoking

• what her carbon monoxide reading means, taking into consideration the time since she last smoked and the number of cigarettes smoked (and when) on the day of the test

If the pregnant woman does not smoke but has a carbon monoxide level of 3 ppm or more, help her to identify the source of carbon monoxide and reduce it. (Other sources include household or other secondhand smoke, heating appliances or traffic emissions.)

If the pregnant woman has a high carbon monoxide reading (more than 10 ppm) but says she does not smoke:

• advise her about possible carbon monoxide poisoning
• ask her to contact the Gas Emergency Line (0800 111 999) for gas safety advice
• phrase any further questions about smoking sensitively to encourage a frank discussion

Record carbon monoxide level and any feedback given in the pregnant woman's antenatal records. If her antenatal records are not available locally, use local protocols to record this information

Notes:

• a carbon monoxide (CO) test is an immediate and non-invasive biochemical method for helping to assess whether or not someone smokes. However, it is unclear as to what constitutes the best cut-off point for determining smoking status
  • some suggest a CO level as low as 3 parts per million (ppm), others use a cut-off point of 6-10 ppm
    • it is important to note that CO quickly disappears from expired breath (the level can fall by 50% in less than 4 hours). As a result, low levels of smoking may go undetected and may be indistinguishable from passive smoking
    • conversely, environmental factors such as traffic emissions or leaky gas appliances may cause a high CO reading - as may lactose intolerance. When trying to identify pregnant women who smoke, it is best to use a low cut-off point to avoid missing someone who may need help to quit
      
      
• "..Most current evidence uses carbon monoxide levels of 4 parts per million (ppm) as the cut-off for referral. Based on this and their expertise, the committee recommended that a carbon monoxide reading of 4 ppm or above would be an appropriate level to automatically refer women for stop-smoking support. This also aligns with the NHS Saving Babies' Lives Care Bundle..." (1)

Reference:

• NICE (November 2021). Tobacco: preventing uptake, promoting quitting and treating dependence