Surgical Research
Open AccessUnilateral Breastfeeding as a Risk Factor for Breast Cancer Development in Lactating Mothers: A Prospective Cohort Study
Authors: Salah Ahmed Binziad, Mohammed Abdulla Baamer, Motaaz Mohammed AL Yazidi.
Abstract
Background: Breastfeeding is widely recommended for infant and maternal health; WHO and AAP guidelines advise exclusive breastfeeding for about 6 months [1]. Prolonged lactation is generally protective against breast cancer [2]. However, at our center we observed lactating mothers who fed predominantly from one breast often developed cancer in the underused breast. This study examines whether one-sided breastfeeding is associated with higher breast cancer incidence in the no suckled or less-used breast.
Methods: In this prospective cohort, we enrolled n = 449 lactating women diagnosed with primary breast cancer between January 2013 and June 2025 at Hadhramout Cancer Center and Al-Arab University Hospitals (Yemen). Detailed breastfeeding behavior were obtained and classified as exclusive unilateral (one breast only), less-suckled (favoring one side), bilateral feeding, or non-feeding, demographic factors, and tumor characteristics were collected. We used χ² tests to assess associations between feeding laterality and tumor side (p<0.05 considered significant). The study was approved by HUCOM Ethics Committee (HUCOM 2013-6) and all participants gave informed consent.
Results: Of 449 women, 111 (24.7%) had cancer in an unsuckled breast (in mothers who exclusively fed one side) and 139 (30.96%) in a less-used breast (in partial unilateral feeders). Another 121 cases (26.95%) occurred in one breast of bilateral feeders, and 78 (17.37%) in one breast of non-breastfeeding women. These distributions differed highly significantly (Pearson χ² = 214.4, p<0.001). In mothers who exclusively breastfed one side, 85% of tumors were in the unsuckled breast (vs. 15% in the suckled breast; p<0.001). Common reasons for one-sided feeding were nipple/breast trauma or infection, infant or maternal preference, and pre-existing breast conditions.
Conclusion: Asymmetrical breastfeeding practices are significantly associated with an increased risk of breast cancer development in the underutilized breast. The findings are biologically plausible: milk stasis and impaired clearance of epithelial cells in the unsuckled breast may foster carcinogenesis [3,4]. Clinicians should encourage bilateral feeding and monitor underused breasts. Further research is needed to confirm these results and clarify underlying mechanisms.
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