Introduction: Breast density is a critical factor in mammography, influencing both cancer risk and detection accuracy. This study aims to determine the prevalence of various breast composition types in screening mammography and examine associations with parity and breastfeeding history among patients at Tabriz University of Medical Sciences.

Methods: This cross-sectional study included 350 women who underwent screening mammography. Breast composition was categorized into four types (A, B, C, D), and data on parity and breastfeeding were collected. Statistical analyses evaluated the associations between breast density types and reproductive factors, using a significance threshold of p < 0.05.

Results: The most frequent breast density types were Type B (44%) and Type C (43.4%), followed by Types A (4.6%) and D (8%). Higher density (Type C) was more common in nulliparous women (50%), but the association was not statistically significant (p = 0.061). Breast density was significantly higher among women who had not breastfed, with a p-value of 0.028.

Conclusion: This study suggests a significant association between breastfeeding history and lower breast density, highlighting breastfeeding’s potential impact on breast tissue composition and possibly reducing cancer risk. Although parity did not show a statistically significant relationship with breast density, reproductive history should be considered in mammographic screening and risk assessment.