INTRODUCTION Online forums provide an environment for peer discussions to anonymously share experiences about sensitive topics. In this article we explore discussions about alcohol use during pregnancy, including representations of 'appropriate' behaviour and risks, in relation to alcohol use.

METHODS We sampled Mumsnet posts from 2016 to 2021 and analysed these using a two-staged approach: describing the content of original posts and employing discourse analysis on the entire thread which focused on unpacking the significance, activity and identity within the discourse.

RESULTS Seventy-three threads with 1554 replies analysed. Users engaged with different sources of evidence and mentioned guidelines and scientific sources, though most commonly provided, requested and appreciated anecdotal information. Risk was discussed in several ways but all users engaged with 'othering' drinking they perceived as risky. Only a few prescribed risks to any and all levels of drinking. There was a lack of knowledge around drinking while trying to conceive and early pregnancy. Expectations and norms of behaviour during pregnancy engaged in a 'good motherhood' discourse. Users positioned their drinking according to perceived norms through language choices; when not pregnant (or unknowingly pregnant) being 'plastered' was justified but when pregnant drinking only 'sips' or 'tiny' quantities of alcohol was considered appropriate.

DISCUSSION AND CONCLUSIONS Forum users demonstrated a desire to adhere to 'responsible motherhood', which did not equate to abstinence if consumption was perceived as acceptable and justified. Future research should explore information needs and effective approaches to health communication for pregnant women or those planning pregnancy.