Introduction: While numerous barriers to smoking cessation in pregnancy have been identified, less is known about the role of pregnant smokers’ beliefs in promoting and inhibiting abstinence. This study explored these beliefs and how they might interact with psychosocial factors related to pregnancy and antenatal care.

Methods: In-depth face-to-face semi-structured interviews were conducted with 20 women with experience of prenatal smoking. Grounded theory and the constant comparative approach guided the analysis towards a theoretical explanation of the women's experiences.

Results: Cognitive dissonance generated by the discrepancy between smoking-related prenatal harm beliefs and continued smoking was a strong motivator to quit. However, difficulty in quitting led many to resolve this dissonance by endorsing disengagement beliefs which downplayed the threat of smoking. Four main types of disengagement belief were identified. The tendency to endorse disengagement beliefs appeared to be influenced by two factors: uncertainty about how smoking caused foetal harm and reassurance from health professionals and others that reduced smoking was sufficient for harm minimisation.

Conclusions: Disengagement belief endorsement is common among pregnant smokers and enables the justification of continued smoking, potentially hindering efforts to quit. Increased promotion of complete abstinence by antenatal care professionals and health education interventions targeting risk comprehension and disengagement belief endorsement should be considered to promote greater efforts to quit among pregnant smokers.