Background The aim of this study was to determine the prevalence and analyze the factors associated with food insecurity during gestation in a maternal-infant cohort in Rio Branco, Acre, Brazilian Western Amazon.Methods A population-based cross-sectional study was conducted with parturients from a maternal-infant cohort in Rio Branco, located in the western Brazilian Amazon. The dependent variable food insecurity was obtained through the Brazilian Scale of Food Insecurity, and associated factors were identified through multiple logistic regression.Results The prevalence of food insecurity in pregnancy was of 34.8% (IC95% = 32.2% - 37.5%). Regarding severity, the prevalence of mild food insecurity was 24.6% (95% CI = 22.3% - 27.0%), moderate food insecurity was 4.8% (95% CI = 3.6% - 6.0%), and severe food insecurity was 5.4% (95% CI = 4.3% - 6.8%). In the final multiple model, the factors directly associated with food insecurity were the presence of open sewage in the peridomestic environment (OR = 1.64; 95% CI: 1.21 - 2.22); belonging to economic classes C, D and E (OR = 1.99; 95% CI: 1.35 - 2.94); being an income transfer program beneficiary (OR = 1.65; 95% CI: 1.18 - 2.30), while the factors inversely associated with FI were schooling equal to or greater than 8 years (OR = 0.66; 95% CI: 0.49 - 0.90); having a partner (OR = 0.56; 95% CI: 0.39 - 0.79); primigestation (OR = 0.59; 95% CI: 0.44 - 0.78) and regular consumption of fruits and vegetables during pregnancy (OR = 0.63, 95% CI: 0.45 - 0.88).Conclusions Despite the existence of income transfer programs, regular consumption of fruits and vegetables is still relatively low and was associated with food insecurity in pregnant women. These findings reinforce the need for the ratification of actions aimed at the domestic economy in the income transfer programs and the development of actions of food and nutritional education in the gestational period.