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This is a plain English summary of an original research article. The views expressed are those of the author(s) and reviewer(s) at the time of publication.

An evidence based stop-smoking intervention called “BabyClear” increased the chance that pregnant smokers in North East England managed to ‘quit’ smoking by the time of delivery by around 80%. It cost £952 for each extra woman who stopped.

Smoking in pregnancy is associated with adverse pregnancy outcomes, but pregnant women continue to smoke, particularly in more deprived areas.

The key feature of BabyClear was that an objective carbon monoxide measurement was undertaken by midwives for all pregnant women at booking. It was designed to help implement NICE guidance and improve identification of pregnant smokers and included an opt-out referral to Stop Smoking services.

The study compared the periods before and after the introduction of BabyClear in North East England in 2012/13. It found improved referral and quit rates, and demonstrated that babies of mothers who successfully stopped smoking had similar birthweight to non-smokers. However, the study design can’t prove BabyClear was the single cause for the changes.

BabyClear may also not help reduce health inequalities. There were few women recruited to this study living in the most deprived areas, but these were half as likely to quit as others, a national problem that remains unsolved.

Why was this study needed?

The Better Beginnings review highlights that smoking in pregnancy is the greatest modifiable risk factor for adverse pregnancy outcomes. However, in some areas of England, such as the North East, around one in four expectant mothers smoke.

Free NHS Stop Smoking Services are very effective, but rely on close collaboration with maternity services to work best. This includes systematic referral pathways and responsive communication between the two organisations.

In 2015/16 the cost of all prescription items used to help people quit smoking in England was £33.2 million. The average cost of a stop smoking prescription item is £29.

Despite 2010 NICE guidance on how this should work, it doesn’t always happen in reality.

BabyClear is a complex intervention designed using existing knowledge of what works to help pregnant women stop smoking. It includes training midwives to monitor carbon monoxide in all pregnant women, an opt-out referral system for all smokers, and improved referral pathways and communications between midwives and Stop Smoking staff.

The study was designed to test if BabyClear increased referral rates, helped more women to quit. It also tested whether it was good value for money in the NHS.

What did this study do?

The NIHR-funded study analysed the medical and administrative records of 37,726 women who gave birth in North East England before, and up to four months after, implementing the BabyClear intervention in 2012/13.

Researchers collected information on date of referral to stop smoking services, appointments and quit status at four weeks. They used maternal NHS number to link data on smoking status at antenatal booking and delivery, with maternal and new born outcomes. Analyses took account of level of local deprivation. Referral to smoking cessation services was also tracked throughout the study.

Smoking in pregnancy averaged 28%.

The study had no control group meaning BabyClear may not be the only reason for any changes seen. Other local smoking policy changes, media stories, or any other uncontrolled events may have contributed to the results, outside of the BabyClear intervention itself.

What did it find?

  • Stop smoking services referrals were more than twice as likely four months after the intervention than before (incidence rate ratio, IRR 2.47, 95% confidence interval [CI] 2.16 to 2.81). Referral increases varied a lot by hospital catchment area, from a modest rise (IRR 1.29) to a very large rise (IRR 6.21).
  • The intervention increased the chance of quitting before delivery by 81% in all women referred to stop smoking services (odds ratio [OR] 1.81, 95%CI 1.55 to 2.12). This chance increased if there was a recorded referral (OR 3.23, 95%CI 2.99 to 3.71), or the woman had a recorded quit attempt (OR 4.18, 95%CI 3.53 to 4.94), both signs they had taken up the referral offer and taken some action to quit.
  • Pregnant women living in most deprived areas (only 1.7% of those recruited) were half as likely to quit compared with those in wealthier areas (OR 0.52, 95% CI 0.42 to 0.65). Most women in the study came from more affluent areas.
  • Babies born to women who did not smoke during pregnancy were around 260g heavier at full term than those born to women who smoked throughout pregnancy. Women who quit smoking by delivery had babies with similar birth weights to non-smokers.
  • The additional cost of the intervention was £31 per delivery, and £952 per extra successful quitter. This cost will vary depending on local smoking prevalence.

What does current guidance say on this issue?

2010 NICE guidance on stopping smoking in pregnancy and childbirth recommends referring all pregnant women who smoke, or have stopped smoking within the last two weeks, to NHS Stop Smoking Services.

NICE also say to refer those with a carbon monoxide reading of 7 parts per million (ppm) or above, though light or infrequent smokers should also be referred, even if they register a lower reading, for example, 3 ppm.

The BabyClear referral criterion in the study was different. It referred anyone with a carbon monoxide reading above 4 ppm to stop smoking services, irrespective of self-reported smoking status.

What are the implications?

BabyClear appears to be an effective way of helping more pregnant smokers to quit, but specific impact and total costs will vary locally according to baseline smoking rates.

For a general population it may not help address inequalities in health outcomes. For example, few women living in the most deprived areas were recruited to this study and were half as likely to quit as others.

The £952 cost per quitter was based on a smoking prevalence of 28% and the average intervention impact, which also varied across different study locations.

The study implemented BabyClear in 2012/13. More recent case studies of implementation and impact may be available to better inform local implementation and best practice.

A recent review published in February 2017 of NIHR evidence highlights a range of research studies evaluation health promotion interventions during pregnancy, including smoking cessation.


Citation and Funding

Bell R, Glinianaia SV, Waal ZV, et al. Evaluation of a complex healthcare intervention to increase smoking cessation in pregnant women: interrupted time series analysis with economic evaluation. Tob Control. 2017. [Epub ahead of print].

This project was independently funded by the National Institute for Health Research School for Public Health Research (SPHR).



NICE. Smoking: stopping in pregnancy and after childbirth. PH26. London: National institute for Health and Care Excellence; 2010.

NIHR Themed Review. Better beginnings: improving health for pregnancy. Southampton: National Institute for Health Research Dissemination Centre; 2017.

NHS Digital. Statistics on NHS Stop Smoking services. England, April 2015 to March 2016. Leeds: NHS Digital; 2016.

Produced by the University of Southampton and Bazian on behalf of NIHR through the NIHR Dissemination Centre


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The BabyClear package is a complex intervention designed to strengthen links between antenatal service providers and community based, local authority funded, stop smoking services. It provided:
  • Skills training for maternity staff, smoking cessation advisors and administrators.
  • Specific training and support material for midwives who implement universal carbon monoxide monitoring at the antenatal booking appointment.
  • Routine opt-out referral for smoking cessation advice was offered to any woman with a carbon monoxide recording above four parts per million.
  • Training in communication skills, including approaches to introduce carbon monoxide monitoring to women, using a behavioural approach was provided.
  • Carbon monoxide monitors and referral forms were provided to all participating trusts.
  • An explicit referral pathway and follow-up protocol for smoking cessation services were introduced.
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