Is it safe to vape? Analysing online forums discussing e-cigarette use during pregnancy Introduction: Electronic cigarette (e-cigarette) use, or vaping, is increasing against a backdrop of declining smoking rates. E-cigarettes contain fewer toxicants than cigarettes but their appearance and mode of use has the potential to satisfy the habitual aspects of smoking. To date, we know little about lay perceptions of the safety of using e-cigarettes in pregnancy. Methods: We conducted a thematic discourse analysis of 13 online discussion forum threads that discussed e-cigarette use during pregnancy. We focussed on the major discursive strategies that forum posters used to debate the safety of e-cigarette use during pregnancy. Results: We identified three distinct ways in which forum posters debated the safety of using e-cigarettes during pregnancy: (1) Quitting (nicotine) cold-turkey is unsafe; (2) vaping is the lesser of two evils; (3) vaping is not worth the risk. Conclusion: Discussions about the safety of e-cigarettes drew on the premise that (1) immediate cessation of nicotine was potentially harmful and unsafe, (2) e-cigarettes were a harm reduction tool, or (3) vaping could be dangerous and should be avoided. While these arguments are not necessarily specific to pregnancy (beside mentions of foetal-specific risks), this analysis points to the need to educate and support women about harm reduction options. Implications: Health professionals should be aware that some women may be currently using or considering using e-cigarettes in an effort to quit or reduce smoking. It is important health professionals are equipped to educate women with accurate up-to-date and balanced information about the risks and benefits of e-cigarette use during pregnancy.