BACKGROUND: Maternal nutrition during pregnancy is crucial to ensure positive outcomes for both the mother and newborn. Despite its importance, maternal nutritional status remains poor, particularly in low- and middle-income countries, where social, cultural and economic factors play a pivotal role. This study assessed the adequacy of energy and dietary nutrient intake among Sri Lankan pregnant women compared to their dietary reference intakes. METHODS: This study was part of the Sri Lanka Mother and Newborn Growth study, a nationwide prospective cohort of 2000 pregnant women. We prospectively investigated maternal dietary intake using a validated food frequency questionnaire during the first, second and third trimesters. RESULTS: We observed an imbalanced macronutrient distribution, with carbohydrates contributing over 67% of total median energy intake, while protein and fat contributed approximately 11% and 17%, respectively. Ethnic and socio-economic disparities in energy and macronutrient intake were notable. The Sinhalese ethnic group showed the highest median percentage of energy consumption derived from carbohydrates at 68.0% (IQR: 64.6%‒71.1%), significantly exceeding the intake of Tamil and Moor groups. Estate residents reported the lowest proportion of energy from protein (10.6%, IQR: 10.1%‒11.3%), which was significantly lower than the intakes of urban and rural residents. Additionally, women in the lowest income group had a lower total energy intake (1871 kcal/day, IQR: 1464-2392) than those in higher income groups, highlighting socio-economic influences on maternal nutrition. Micronutrient deficiencies were pervasive, particularly for vitamin B2 (88.6%-91.0%), folate (99.3%-99.8%), vitamin B12 (97.8%-99.5%), calcium (80.8%-91.4%) and iron (91.1%-96.5%). Sodium intake exceeded recommended levels for over 75% of women across all trimesters. CONCLUSION: Imbalances in macronutrient intake and widespread micronutrient deficiencies among Sri Lankan pregnant women underscore the urgent need for interventions targeting maternal nutrition. Addressing socio-economic disparities is critical to improving maternal and neonatal health outcomes.