Objective: to identify the determining factors for pregnant women's knowledge about breastfeeding. Methodology: This is an epidemiological, exploratory, cross-sectional study carried out with pregnant women in a municipality in the state of Paraná. The collection was carried out with pregnant women, through the application of a questionnaire from December 2021 to April 2022. The data were analyzed using descriptive and inferential statistics. Results: 384 pregnant women, with an average age of 27.8 years, participated in the study. Those with a level of education <8 years (OR: 2.4 (1.12 - 5.24)), women with one or more children (OR: 5.2) had the greatest chance of not knowing about breastfeeding. (2.30-11.65)), primiparous (OR: 5.6 (2.52-12.62)), with urinary tract infection in the current pregnancy (OR: 2.3 (1.06-4, 95)), submitted to a previous cesarean section (OR: 4.8 (1.77-12.88)) and who are unaware of the mode of delivery: vaginal delivery (OR: 7.6 (3.66-15.68) )) and cesarean delivery (9.1 (OR: 4.43- 18.76)). Conclusion: The prenatal consultation should be an effective tool for actions to promote breastfeeding with pregnant women.