Previous studies have shown cesarean section (C-section) and antibiotic use in the infantile period lead to chronic diseases in later life. It is also known that breastfeeding, which forms the basal system of immunity, is a protector in neonates. In this study, we aimed to investigate the association between breastfeeding, antibiotic use, C-section, and premature atherosclerosis. A total of 100 patients who underwent coronary angiography and had stenosis in at least 1 epicardial vessel and 100 controls with normal coronaries were included in the study. In addition to traditional risk factors, type of delivery, breast milk intake and duration, and antibiotic use and frequency were evaluated for each participant. Lipid profile was added to the study procedure. Angiographic images of the study groups were examined to calculate the Gensini score. Smoking, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and family history were different between the groups. In the control group, 3 were born via C-section, whereas 26 were born via C-section in the atherosclerosis group (p<0.001). Breast milk intake and duration was also significantly higher in the control group (p=0.018). Antibiotic use was less in the control group, but there was no statistically significant difference (p=0.099). In multivariate logistic regression analysis, diabetes mellitus, smoking, and C-section were predictors of atherosclerosis (p=0.036, p=0.001, and p=0.003, respectively). In receiver operating characteristics curve analysis, the ability of C-section to predict premature atherosclerosis was superior to diabetes but not to smoking (area under curve, 0.607; p=0.023). Mode of delivery and breast milk intake should be evaluated and considered among the risk factors of premature atherosclerosis.