OBJECTIVE: to examine the social correlates of pre-pregnancy overweight and obesity in an Australian population-based sample and consider implications for intervention effectiveness during pregnancy. DESIGN: population-based survey distributed by hospitals to women 6 months after birth. SETTING: two states of Australia. PARTICIPANTS: women who gave birth in Victoria and South Australia in September/October 2007. MEASUREMENTS AND FINDINGS: surveys were completed by 4,366 women. Pre-pregnancy body mass index (BMI) was calculated from women's self-reported weight in kilograms/(height in metres)(2). Results showed high rates of overweight (22%) and obesity (14%) among Australian women entering pregnancy. After adjusting for other factors in the model, pre-pregnancy obesity was significantly associated with lower household income levels, less education, the experience of financial stress in pregnancy and increasing parity. KEY CONCLUSIONS: to date, there is little evidence to support the efficacy of interventions to manage problematic weight in pregnancy. Applying a social disparities lens to obesity in pregnancy challenges us to consider social factors that may seem distal to obesity but are highly relevant to efficacious intervention. IMPLICATIONS FOR PRACTICE: pregnancy care offers an opportunity to address social issues on the pathway to obesity. Current clinical care guidelines on maternal overweight and obesity in pregnancy rarely consider social contexts that place some women at risk and are a likely impediment to efficacious intervention.