Nutrition during pregnancy and postpartum is critical in maternal and infant health, with poor dietary intake during this period contributing to adverse outcomes and long-term health risks.(1) Dietary intake is influenced by behavioural, physiological, and social factors,(2) and understanding the patterns, and their determinants, can inform targeted nutrition interventions. This study aimed to assess changes in diet quality and food and nutrient intakes from pregnancy to one year postpartum in Australian women and compare to national nutrition recommendations. Associations between diet quality, sociodemographic and health characteristics were also investigated. This study was an analysis of data from the ORIGINS pregnancy cohort (2017-2022). Women were included if they had complete dietary data at both timepoints, were aged ≥19 years, and were not pregnant one year postpartum. Dietary intake was assessed via the Australian Eating Survey food frequency questionnaire and diet quality was assessed using the Australian Recommended Food Score (ARFS). Sociodemographic data were self-reported; clinical health data were extracted from hospital medical records. Paired sample t-tests analysed changes in diet quality and intake. Linear regression estimated associations between maternal characteristics and diet quality, with adjustment for covariates. Food group and nutrient intakes were compared to recommendations in the Australian Guide to Healthy Eating and Nutrient Reference Values. Among 337 women (33.1 (4.5) years, 49.9% Australian-born, 51.3% university educated), mean (95% CI) diet quality was suboptimal during pregnancy and one year postpartum (ARFS 34.0 (33.0, 35.0) vs. 34.8 (33.8, 35.8) points out of 73, p = 0.038). One year postpartum, participants reported consuming more vegetables, meat, protein, and retinol equivalents, but less fruit, dairy, carbohydrate, saturated fat, iodine, and folate (p < 0.05). Across both timepoints, alignment with recommendations was poor for all food groups, macronutrients and key micronutrients. None of the women met the daily intake targets for all five food groups during pregnancy, and only one woman met the targets one year postpartum. Lower diet quality during and after pregnancy was linked to not having had a university education, and a higher pre-pregnancy BMI. Postpartum, younger age and lower income was also associated with poorer diet quality and having a BMI in the overweight category before pregnancy (p<0.05). Findings underscore persistent nutritional inadequacies and social disparities among pregnant and postpartum women in Australia and provide evidence to support updates to national dietary guidelines and the development of targeted nutrition interventions, particularly for women experiencing socioeconomic disadvantage.