Investigating the utility of the COM-B and TM model to explain changes in eating behaviour during pregnancy: A longitudinal cohort study

Objectives: Pregnancy has been described as a ‘teachable moment’ for behaviour change, which presents an important opportunity for health promotion within antenatal care settings. However, no pregnancy-specific model has been developed or tested in the context of health behaviour change during pregnancy. This study aimed to investigate and compare the utility of the Capability-Opportunity-Motivation Behaviour (COM-B) and Teachable Moments (TM) models, to explain health behaviour change during pregnancy, within the context of eating behaviour. Design: Longitudinal cohort studyMethods: Five hundred and sixteen women completed a survey at between 12-16 weeks gestation (T1). Follow-up data were collected at 20-24 weeks (T2), 36-40 weeks (T3), and 6-12 weeks postnatally (T4). The primary outcome was eating behaviour. To assess the utility of the COM-B model, perceived capability, opportunity, and motivation to eat healthily were measured. To assess the utility of the TM model, risk perceptions, self-image, and affective response were measured. Results: Overall, the COM-B model explained 18.4% of the variance in eating behaviour, whilst the TM model explained 9%. Both models explained the most variance in eating behaviour at T1 and T3, compared with T2 and T4. Small changes were observed in eating behaviour and the model constructs over the time period studied, although these were not clinically meaningful. Conclusions: Neither the COM-B nor TM model provide a satisfactory explanation of eating behaviour during pregnancy, however the findings suggest that certain stages of pregnancy may create more salient opportunities for behaviour change. The findings also support claims that motivation may not play a key role in directing eating behaviour during pregnancy. Further research is needed to explore the role of timing in antenatal behaviour change. The development of a pregnancy-specific model is necessary to optimise understanding of pregnancy as a teachable moment for behaviour change.