Utility of the capability, opportunity, and motivation behaviour (COM-B) model in explaining the negative association between pre-pregnancy body mass index and exclusive breastfeeding at six weeks postpartum.

ABSTRACT

The mechanisms underlying the negative associations between pre-pregnancy body mass index (BMI) and exclusive breastfeeding remain poorly understood. Thus, the study aimed to determine whether the negative associations between high pre-pregnancy BMI and exclusive breastfeeding at six weeks postpartum are mediated by components of the capability, opportunity, and motivation behaviour (COM-B) model. In this prospective observational study, we assigned 360 primiparous women to a pre-pregnancy overweight/obese group (n = 180) and a normal-BMI group (n = 180). A structural equation model was designed to study how capabilities (onset of lactogenesis II, perceived milk supply, breastfeeding knowledge, and postpartum depression), opportunities (pro-breastfeeding hospital practices, social influence, social support), and motivations (breastfeeding intention, breastfeeding self-efficacy, and attitudes towards breastfeeding) affected exclusive breastfeeding at six weeks postpartum in groups of women with different pre-pregnancy BMIs. In all, 342 participants (95.0%) possessed complete data. Women with high pre-pregnancy BMI were less likely to exclusively breastfeed at six weeks postpartum than women with a normal BMI were. We observed a significant negative direct effect of high pre-pregnancy BMI on exclusive breastfeeding at six weeks postpartum and a significantly negative indirect effect of high pre-pregnancy BMI via the explanatory mediating variables of capabilities (onset of lactogenesis II, perceived milk supply, and breastfeeding knowledge) and motivations (breastfeeding self-efficacy) on exclusive breastfeeding at six weeks postpartum. Our findings support certain capabilities (onset of lactogenesis II, perceived milk supply, and breastfeeding knowledge) and motivations (breastfeeding self-efficacy), partially explaining the negative association between high pre-pregnancy BMI and exclusive breastfeeding outcome. We suggest that interventions aimed at promoting exclusive breastfeeding among women with high pre-pregnancy BMI should address the capacity and motivation factors specific to this population.