What does the latest evidence tell us about the impact of vaping during pregnancy?

In this blog, Professor Linda Bauld, Bruce and John Usher Chair of Public Health at the University of Edinburgh and Co-Chair of the Smoking in Pregnancy Challenge Group summarises the current evidence on the impact of vaping during pregnancy and what health professionals should keep in mind when advising pregnant women.

Concerns have been raised by maternity professionals about the findings from a 2025 meta-analysis by Vallée et al published in Women and Birth: Maternal vaping and pregnancy adverse outcomes: A systematic review and meta-analysis. Given the importance of maternal and baby safety, it is worth looking closely at what this review does – and does not – tell us. 

While caution is entirely appropriate in this area, there are important limitations in the Vallée review that affect how its findings should be interpreted. The Smoking in Pregnancy Challenge Group’s position remains clear: if the alternative is smoking, pregnant women should be supported to vape.

The Smoking in Pregnancy Challenge Group has developed guidance to support health professionals to provide evidence-based advice to pregnant women who smoke or vape. This has been endorsed by the Royal College of Midwives, Royal College of Nursing, Royal College of Obstetricians and Gynaecologists, Sands, Tommy’s and the Lullaby Trust among others. This guidance will be updated as new evidence emerges. 

The Challenge Group guidance states that:

• While licensed nicotine replacement (NRT) products such as patches, gum and inhalators are the NICE-recommended option, vapes appear to be more effective for smoking cessation than nicotine patches. Regular use of vapes or NRT during pregnancy does not appear to be associated with any adverse effects in mothers or their babies. If a pregnant woman chooses to vape and if that helps her to quit smoking and stay smokefree, she should be supported to do so.

The key limitation of the Vallée paper is the failure to control for former smoking among pregnant vapers – both in the studies included in the meta-analysis and in the analysis itself. The authors acknowledge that the studies included often “did not differentiate between ex-smokers and current smokers.” This makes it impossible to know whether the findings are a result of vaping or previous/concurrent smoking. Given the fact that most adult vapers are current or former smokers, it is likely that the findings are heavily influenced by unrecorded smoking among the vaping cohort. 

A 2024 systematic review of the impacts of vaping during pregnancy led by Prof Michael Ussher reviewed many of the same studies as the Vallée paper and found that “none of the studies […], adequately assessed exposure to nicotine and tobacco products, especially cigarette smoking.” They concluded that “the quality of the evidence limits conclusions. Without adequate assessment of exposure to vaping and smoking, findings cannot be attributed to behaviour as many who vape will have smoked and many who vape may do so at low levels.”

This is a common challenge when undertaking meta-analyses or systematic reviews into the health impact of vaping. Many studies of vaping do a poor job of controlling for previous/current smoking, making it difficult to know whether the findings are due to vaping or smoking. Unfortunately, this is not always communicated clearly by researchers. 

Additionally, many of the studies included in the meta-analysis were cross-sectional, meaning that they cannot demonstrate a causal link between vaping and health outcomes. 

The conclusions of the Vallée review are not supported by evidence from the only NIHR-funded high-quality randomised control trial (RCT) – which I was involved in – examining the safety and efficacy of using vapes to quit smoking during pregnancy. This found that nicotine vapes were more effective than nicotine patches for quitting smoking and did not increase the risk of adverse maternal outcomes (relative to nicotine patches). We conducted a secondary analysis comparing outcomes in participants who regularly used a nicotine product (vapes or patches) but didn’t smoke with those who didn’t use any nicotine or tobacco products. There was no difference in birthweight between the two groups and regular use of vapes/NRT was not associated with any adverse effects in mothers or their babies.

In summary, the evidence-based recommendation from the Smoking in Pregnancy Challenge Group continues to be that pregnant women should be supported to vape if the alternative is smoking. We will continue to keep this recommendation under review as the evidence develops.