Explainers

Smoking in Pregnancy: A Danger to Mother and Baby


Smoking in pregnancy poses a significant health problem for both mother and baby.

Many women who smoke will quit by themselves before becoming pregnant and others will stop once their pregnancy is confirmed. For some women, however, considerable help is needed to stop smoking successfully (NCSCT 2018).

The research evidence is clear: cigarettes contain multiple harmful substances, and women who smoke during pregnancy are more likely to have babies with birth defects than non-smokers.

As smoking in pregnancy adversely affects so many different aspects of health, it remains one of the greatest factors that could potentially improve birth outcomes (NIRH 2017).

Risks for the Mother

Dechanet et al. (2011) report that over the past few decades the prevalence of smoking amongst women of reproductive age has actually increased despite greater public awareness of the risks.

It’s well known, for example, that smoking can impair fertility and in addition to the general risks of smoking, pregnant women also face additional pregnancy-related health risks including;

  • Ectopic pregnancy
  • Placenta praevia
  • Pre-eclampsia
  • Deep vein thrombosis.

(McEwen 2016)

Risks for the Foetus

Smoking while pregnant is well known to be harmful to the growing foetus with an increased risk of miscarriage, higher rates of IVF failures, intrauterine growth retardation and premature birth. More recently the spotlight has also focused on the increased risks of birth defects.

For example, in a recent systematic review, Dechanet et al. (2011) found significant positive associations between maternal smoking and the following birth defects, compared to pregnant non-smokers.

A Summary of the Increased Chances of Birth Defects Amongst Pregnant Smokers:

  • Cardiovascular/heart defects: pregnant smokers had a 9% increase.
  • Muscle/skeletal defects: pregnant smokers had a 16% increase.
  • Limb reduction defects: pregnant smokers had a 26% increase.
  • Missing/extra digits: pregnant smokers had an 18% increase.
  • Clubfoot: pregnant smokers had a 28% increase.
  • Facial defects: pregnant smokers had a 19% increase.
  • Eye defects: pregnant smokers had a 25% increase.
  • Cleft palate: pregnant smokers had a 28% increase.
  • Gastrointestinal defects: pregnant smokers had a 27% increase.
  • Gastroschis: pregnant smokers had a 50% increased risk.
  • Rectum abnormalities: pregnant smokers had a 20% increased risk.
  • Hernia: pregnant smokers had a 40% increased risk.
  • Undescended testes: pregnant smokers had a 13% increased risk.

(Dechanet et al. 2011)

Not all researchers agree with Dechanet’s findings, however, and there is a clear need for further research in this area.

What most will agree on though, is that nicotine, together with the multiple carcinogenic pollutants found in cigarettes is detrimental to healthy foetal development. It’s generally agreed that unless further research proves otherwise public health information should make women aware of these potential risks and provide practical help and encouragement to quit smoking early in pregnancy, and ideally prior to conception.

Nicotine Replacement Therapy May Not be the Answer

As nicotine addiction is the factor that stops many women from giving up smoking during pregnancy, use of nicotine replacement therapy (NRT) has been suggested as a lower risk to the foetus. However, the safety of NRT has not yet been well documented and many researchers have conflicting opinions about its potential to harm the foetus.

Wickström (2007) suggests that this is because the causative agents for the harmful effects of smoking have been difficult to determine as cigarette smoke contains thousands of biologically active compounds. Some of these substances are well known to be foetal toxins, for example, carbon monoxide and nicotine. The effect of many other potential toxins have yet to be effectively researched.

In theory, nicotine replacement should be safer than smoking, but as several animal studies have shown, the total dose of nicotine that the foetus is exposed to is a significant factor for brain development. Since conventional doses of NRT may be less effective in pregnancy, the higher doses of nicotine needed may exceed the threshold for alterations in brain development and cause foetal harm.

That said, there is a general view that NRT during pregnancy is safer than smoking. At the same time, it’s widely acknowledged that a total abstinence from all forms of nicotine should be advised to pregnant women from pre-conception through to birth.

Although pregnancy is often a strong motivator for smoking cessation, many women continue to smoke and more effective strategies to help them become non-smokers are urgently needed.

Traditional behavioural support provided by prenatal stop-smoking programs only results in a relatively modest reduction in smoking cessation rates. This is why, based on the effectiveness of NRT in the general population, it’s thought that nicotine replacement therapy in association with behavioural therapy, counselling, or cognitive behavioural therapy may be a possible way forward.
However, controversy remains about whether or not care providers should recommend NRT during pregnancy because of persistent concerns about its safety and effectiveness (Osadchy et al. 2009).

How Can Nurses and Midwives Help?

It’s now widely accepted that any contact with a pregnant woman from preconception through to postnatal visits, provides an opportunity to give advice on smoking cessation, but many midwives remain unclear on what exactly this advice should be.

In the UK, the National Institute of Clinical Excellence (NICE 2010) suggests that practitioners should follow the ‘ask, advise and act‘ sequence to help mothers become non-smokers.

  • Ask and record smoking status, verifying it with a carbon monoxide monitor
  • Advise women briefly about the importance of quitting
  • Act to refer them to quit services

(ASH 2017)

Although these guidelines are clear about the need to help mothers stop smoking, it’s also clear that practitioners lack confidence and training on how to communicate this message in a way that actually achieves behavioural change.

Similar research carried out by Longman (2018), explored the enablers and barriers to implementation of the Australian smoking cessation in pregnancy guidelines. These guidelines suggest that practitioners follow ‘the 5 A’s of cessation.’

  • Ask
  • Advise
  • Assess
  • Assist
  • Arrange to follow up

Again, barriers to success include knowledge and skills gaps, reluctance to engage in ‘difficult conversations’, as well as perceiving smoking as a social activity.

Finding innovative and effective ways to reduce smoking in pregnancy remains a priority. To date, there is still relatively little evidence on the efficacy of smoking cessation interventions before, or after pregnancy, or on preventing relapse after quitting during pregnancy (NIRH 2017).

Smoking remains one of the few modifiable risk factors in pregnancy, yet it continues to be a worldwide public health concern.

From the mothers’ point of view, this is an invisible problem and whilst smoking continues to be viewed as an acceptable social activity rather than as an addiction, it’s unlikely that significant progress will be made.

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