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Background: Many factors such as social and behavioral are related to appropriate weight gain during pregnancy, and there is much of importance to find them. The aim of the study was to explore the association of personality traits, with eating behaviors, food intake, maternal weight gain during pregnancy as well as the neonatal birth weight. Methods: This is a longitudinal and cross-sectional study. Eating behaviors were assessed using the Dutch Eating Behavior Questionnaire (DEBQ), and the NEO personality inventory was used to assess personality in pregnant subjects. A validated food frequency questionnaire was used to determine food intake. Three hundred and sixty pregnant subjects from Ahvaz (the capital city of Khuzestan province, Iran) were followed from the 20th week of pregnancy until delivery. Results: High neuroticism was associated with higher consumption of highly energetic foods (p < 0.05) and less consumption of vegetables (p < 0.01), also was related with lower weight gain during pregnancy and neonatal birth weight (p < 0.05). Openness to experience, extraversion and agreeableness were linked with higher consumption of vegetables (p < 0.05). Conscientiousness predicted lower neonatal weight (odds ratio: 1.20, confidence interval: 1.07-1.34, p < 0.01). Conclusions: Identification of personality traits would help to change the lifestyle and improve management guidelines.