Guidelines consistently advise that the best thing a pregnant woman can do is to stop smoking. Now, new research has found that regular use of nicotine replacement products to assist smoking cessation is not associated with adverse events or poor pregnancy outcomes.

“Using nicotine products to stop smoking during pregnancy appeared safe,” Professor Peter Hajek of the Wolfson Institute of Population Health, Queen Mary University of London, and lead researcher of the study told Medscape News UK.

The scientists found that pregnant women who stopped smoking cigarettes and used e-cigarettes and nicotine patches had infants with significantly higher birth weight than smokers, and “not different from abstainers not using nicotine”. The researchers wrote that they “did not detect any risks to pregnancy” from e-cigarettes or nicotine patches used by smokers trying to quit.

The study was funded by the National Institute for Health and Care Research (NIHR) and led by scientists at Queen Mary University of London. It was published in the journal Addiction.

Current Guidance

The prevalence of smoking during pregnancy has been decreasing over time. The smoking rate for pregnant women at the time of birth fell to 9.1% in 2021-2022, the lowest annual rate on record. In 2022-2023, the prevalence had dropped slightly further to 8.8%, but was still higher than the government’s target of 6%.

A landmark review in 2015 led by King’s College London and commissioned by Public Health England found that e-cigarettes had the potential to reduce smoking. It also found that nearly half the population (44.8%) did not realise that e-cigarettes or vapes were much less harmful than smoking. 

Both the Royal College of Obstetricians and Gynaecologists (RCOG) and the NHS currently recommend that pregnant women stop smoking completely, ideally before the fact.

They also suggest that nicotine replacement therapy (NRT) can be an effective aid for pregnant women who want to stop smoking. NICE points out in its recommendations on treating tobacco dependence in pregnant women that “any risks from using NRT are much lower than those of smoking”. 

In 2019, the Royal College of Midwives released a position statement that stated that “E-cigarettes contain some toxins, but at far lower levels than found in tobacco smoke. If a pregnant woman who has been smoking chooses to use an e-cigarette (vaping) and it helps her to quit smoking and stay smokefree, she should be supported to do so”.

Still, Professor Tim Coleman, Smoking in Pregnancy research group, University of Nottingham, who was also involved in the study, said in a press release that “some clinicians are reticent about providing NRT or e-cigarettes in pregnancy”.

Hajek explained that, in animal studies, chronic forced large doses of nicotine led to a range of adverse pregnancy outcomes. This has led to caution among some healthcare professionals. However, he said that studies have shown that this does not translate to self-regulated nicotine doses in humans. 

Building a Foundation of Evidence

Knowledge gaps remain, though. A Cochrane review in 2020 concluded that there was no evidence that NRT had positive or negative impacts on birth outcomes. In 2021, a systematic review concluded that NRT seemed to be associated with higher risk of infantile colic at 6 months similar to that associated with smoking during pregnancy. It also found an association with higher risk of attention-deficit/hyperactivity disorder. The review did not find associations were reported between the use of NRT during pregnancy and other infant health disorders or major congenital anomalies.

In 2023, a study suggested that aerosols from e-cigarettes may contain several newer, potentially toxic compounds, including some known developmental toxicants that may adversely impact both the mother and foetus. However, the authors found that research was limited, with large knowledge gaps regarding the effects of e-cigarette use on maternal and foetal health and birth outcomes.

Hajek said that vapes are more effective for smoking cessation than NRT, but the impacts of their extended use is currently unclear.

NICE emphasises that most smoking-related health problems are caused by other components in tobacco smoke, not by the nicotine.

“The harms to pregnancy from smoking, in late pregnancy at least, seem to be due to other chemicals in tobacco smoke rather than nicotine,” Hajek explained.

Hazel Cheeseman, deputy chief executive at Action on Smoking and Health told Medscape News UK: “Given the significant risks of smoking during pregnancy, it is vital that pregnant smokers are supported to stop.” She said the new study added to the evidence that e-cigarettes are safe and effective for use by pregnant women to quit smoking. 

“There are widespread misperceptions about the risks of nicotine in pregnancy. While smoking is deadly, nicotine on its own does not cause the same harms. These findings should provide reassurance that vaping products and nicotine replacement therapy do not increase the risk of harms during pregnancy and can be safely recommended for smoking cessation,” said Cheeseman.