母乳喂养与乳腺癌风险呈反比关系，但母乳喂养与乳腺摄影密度（MBD）的关联关系尚不清楚。我们调查了母乳喂养与体积测量的MBD（体积百分比密度（VPD），密集体积（DV）和非密集体积（NDV））之间的关联性，并评估了其是否因种族、更年期状态和身体质量指数（BMI）而有所不同。研究人群包括964名女性（67%为非裔白人，29%为非裔黑人），她们在密苏里州圣路易斯华盛顿大学医学院进行了乳腺癌筛查。 VPD，DV和NDV被log10转换。我们进行了多元线性回归模型，该模型对所有参与者和仅对产妇进行了调整，包括年龄，BMI，家族乳腺癌史，种族和初潮年龄。平均年龄为50.7岁。母乳喂养0-6个月的女性的VPD降低了12％，（10 ^β = 0.88，95％CI（0.79,0.98）），与未生育的女性相比。母乳喂养与DV呈反比关系（产妇未母乳喂养：10^β = 0.93，95％CI（0.83,1.04），母乳喂养0-6个月：10^β = 0.91，95％CI（0.79,1.05），母乳喂养7-12个月：10^β = 0.94，95％CI（0.81,1.10），母乳喂养> 12个月：10^β=0.87，95％CI（0.78,0.98），p-trend=0.03）。BMI改变了母乳喂养与VPD之间的关联。母乳喂养0-6个月且BMI < 25kg/m2的女性与未生育的女性相比，VPD更低，但BMI> = 25kg/m2的女性没有关联（p-interaction=0.04）。在这个多样化的研究人群中，母乳喂养与VPD的关联似乎受BMI影响，但不受种族或更年期状态的影响。未来研究探讨母乳喂养与其他乳腺摄影特征的关联性是必要的。

Breastfeeding is inversely associated with breast cancer risk but the associations of breastfeeding with mammographic breast density (MBD) are not clear. We investigated the association between breastfeeding and volumetric measures of MBD (volumetric percent density (VPD), dense volume (DV) and non-dense volume (NDV)) and evaluated whether it differs by race, menopausal status, and body mass index (BMI). The study population was comprised of 964 women (67% non-Hispanic white, 29% non-Hispanic black) who had screening mammography at Washington University School of Medicine, St. Louis, MO. VPD, DV and NDV were log10 transformed. We performed multivariable linear regression models adjusted for age, BMI, family history of breast cancer, race, and age at menarche among all participants and exclusively in parous women. Mean age was 50.7 years. VPD was 12% lower among women who breastfed 0-6 months, (10^β=0.88, 95%CI (0.79,0.98)) compared to nulliparous women. Breastfeeding was inversely associated with DV (parous never breastfed: 10^β=0.93, 95%CI (0.83,1.04), breastfed 0-6 months: 10^β=0.91, 95%CI (0.79,1.05), breastfed 7-12 months: 10^β=0.94, 95%CI (0.81,1.10), breastfed >12 months: 10^β=0.87, 95%CI (0.78,0.98), p-trend=0.03). BMI modified the association between breastfeeding and VPD. Women who breastfed for 0-6 months and had a BMI < 25kg/m2 had lower VPD compared to nulliparous women, but among women with a BMI ≥ 25kg/m2 there was no association (p-interaction=0.04). In this diverse study population, the association of breastfeeding with VPD appears to be modified by BMI, but not by race or menopausal status. Future research exploring the associations of breastfeeding with other mammographic features are needed.