Safety of e‐cigarettes and nicotine patches as stop‐smoking aids in pregnancy: Secondary analysis of the Pregnancy Trial of E-cigarettes and Patches (PREP) randomized controlled trial

Francesca Pesola, Katie Myers Smith, Anna Phillips-Waller, Dunja Przulj, Christopher Griffiths, Robert Walton, Hayden McRobbie, Tim Coleman, Sarah Lewis, Rachel Whitemore, Miranda Clark, Michael Ussher, Lesley Sinclair, Emily Seager, Sue Cooper, Linda Bauld, Felix Naughton, Peter Sasieni, Isaac Manyonda, Peter Hajek

Research output: Contribution to journalArticlepeer-review


Aims: The aim of this study was to examine the safety of e-cigarettes (EC) and nicotine patches (NRT) when used to help pregnant smokers quit. Design: A recent trial of EC versus NRT reported safety outcomes in the randomized arms. We conducted a further analysis based on product use. Setting: Twenty-three hospitals in England and a stop-smoking service in Scotland took part. Participants: The participants comprised 1140 pregnant smokers. Interventions: We compared women using and not using EC and NRT regularly during pregnancy. Measurements: Measurements included nicotine intake compared with baseline, birth weight, other pregnancy outcomes, adverse events, maternal respiratory symptoms and relapse in early abstainers. Findings: Use of EC was more common than use of NRT (47.3% vs 21.6%, P < 0.001). Women who stopped smoking (abstainers) and used EC at the end-of-pregnancy (EOP) reduced their salivary cotinine by 45% [49.3 ng/ml, 95% confidence interval (CI) = −79.8 to −10]. Only one abstainer used NRT at EOP. In dual users, cotinine increased by 19% (24 ng/ml, 95% CI = 3.5–68). In women reporting a reduction of at least 50% in cigarette consumption, cotinine levels increased by 10% in those using nicotine products and by 9% in those who did not. Birth weights in dual users and exclusive smokers were the same (3.1 kg). Birth weight in abstainers using either nicotine product was higher than in smokers [3.3 kg, standard deviation (SD) = 0.7] versus 3.1 kg, SD = 0.6; difference = 0.15 kg, 95% CI = 0.05–0.25) and not different from abstainers not using nicotine products (3.1 kg, SD = 0.8). Abstainers and smokers using nicotine products had no worse pregnancy outcomes or more adverse events than abstainers and smokers not using them. EC users reported more improvements than non-users in cough [adjusted relative risk (aRR) = 0.59, 95% CI = 0.37–0.93] and phlegm (aRR = 0.53, 95% CI = 0.31–0.92), controlling for smoking status. EC or NRT use had no association with relapse. Conclusions: Regular use of e-cigarettes or nicotine patches by pregnant smokers does not appear to be associated with any adverse outcomes.

Original languageEnglish
Early online date17 Jan 2024
Publication statusE-pub ahead of print - 17 Jan 2024


  • Birth weight
  • e-cigarettes
  • nicotine
  • pregnancy
  • safety
  • smoking
  • vaping

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