Smoking in Pregnancy

Clearing the air.

Why don’t governments ban smoking? 

Why do they not pass legislation banning cigarette smoking in every place that has a roof?

Politicians know that smoking is bad for the health of the population and that health budgets are growing exponentially.  So why not reduce expenditure by preventing the many diseases caused by smoking by enacting anti-tobacco legislation?

Several answers suggest themselves.

Firstly, it would require effort to introduce anti-smoking laws and the positive effects are not well documented (until now). Secondly they will make enemies of the powerful tobacco companies. Thirdly, taxes would decline. Fourthly, politicians may perceive that the benefits to health and the subsequent financial savings may be too distant for them to receive the kudos for implementing changes in the law.

But according to new data to new data published in The Lancet (Been et al 2014;383:1549-60) these perceptions could be wrong. In a landmark review the authors tracked the effects of smoke-free legislation on perinatal outcomes and child health. It is well known that smoking can adversely affect the fetus resulting in growth restriction, placental abruption, early delivery and stillbirth, but the impact of smoke-free laws on the epidemiology of these events is now becoming apparent.

Where smoking bans have been implemented the results are striking, with reductions of 10% in preterm birth rates and the number of hospital attendances for asthma in young children dropping by similar proportions. There was also a decrease of 5% in the rate of babies born very growth restricted so both the immediate and long-term financial gains are clear. The authors believe that these differences are achieved as much by the reduction in the inhalation of second-hand smoke as they are with mothers ceasing to smoke.  “Rarely can such a simple intervention improve health and reduce medical costs so swiftly and substantially” (Kalhoran & Glantz Lancet 2014;383:1526-7).

The medical profession has produced proof of the dangers of smoking and now provides evidence that legislation makes economic sense. Should doctors both individually and collectively not try to persuade politicians to enact anti-smoking laws to reduce disease and save money?

The harms of smoking in pregnancy

Although smoking is associated with poor obstetric outcomes, the exact pathophysiology is unclear. New genomic investigations comparing smokers, those who have recently stopped smoking and non-smokers have shown precise defects that are associated with tobacco smoke exposure.

Cells can be examined for markers of apoptosis (which is programmed cell death) and for DNA repair. Placental cells from smokers show evidence of double strand DNA breakage which is a severe form of damage that is not present in the placental cells of non-smokers (Slatter et al Hum Path 2014;45:17-26). In women who stopped smoking the researchers found there was less evidence of DNA damage and normal repair processes were evident, so it seems there is clear benefit in stopping, even as late as the third trimester. They discovered that the communication of this information to smoking pregnant women provided an added incentive for them to move towards smoking cessation.

The problem is that nicotine addiction can be severe and those with a genetic predisposition (now identifiable) find it nigh impossible. Even the knowledge that smoke damages their own bodies and their unborn child’s health, cannot convince some women to stop and half of pre-pregnancy smokers continue throughout pregnancy so researchers have been looking at ways of mitigating the effects on the fetus. By giving half of a cohort of smoking pregnant women 500mg of vitamin C per day it was possible to show in a controlled trial that newborn pulmonary function was improved by such an intervention (McEvoy et al JAMA May 18, 2014.doi:10.1001/jama.2014.5217).

In addition neonates born to smoking mothers receiving the vitamin C had significantly decreased wheezing up to the age of one year. It is tempting to speculate that other long-term effects of exposure to intra-uterine smoke, like lung development and life-long decreases in pulmonary function could also be attenuated by vitamin C administration, but obviously the optimal solution is for mothers-to-be to stop smoking in pregnancy and stay abstinent.

Any diatribe against smoking would be incomplete without a mention of the volumes being written about e-cigarettes.

Far from being harmless alternatives to combustible cigarettes, e-cigarettes or inhaling the vapours created by heating a liquid containing nicotine, flavouring agents and solvents, are also dangerous (Kamerow BMJ 2014;348:g2504).  Vaping these substances gives exposure to the following carcinogens or reproductive toxins: nicotine, acetaldehyde, benzene, cadmium, formaldehyde, isoprene, lead, nickel and toluene. That is on top of measurable amounts of propylene glycol, diethylene glycol and nitrosamines.

It is unsurprising that regulating agencies have placed the same constraints on e-cigarettes as their combustible cousins.  This now includes the FDA in America.

The Americans are pushing hard to reduce their smoking rates (now at 18%) and one of the ways they are trying is the “denormalising” of smoking.  Examples of this thrust are the banning of lighting-up in outdoor public places in New York and the restricting of tobacco sales in pharmacies.  This concept – of health-harming products being sold alongside medicine – seems exclusive to the United States where profits and health measures often collide.  The stakes are high with tobacco use costing the US $120 billion a year in direct heath costs and a further $160 billion in lost productivity (Brennan & Schroeder JAMA 2014;311:1105-6).

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