Quantitative Changes in Breast Density and Mammographic Features Induced by Pregnancy and Lactation: A Longitudinal Study.

Objective: Quantitative changes in mammographic properties during pregnancy and lactation remain underexplored. Therefore, the purpose of this study was to quantify mammographic changes in the breast from prepregnancy through lactation to postweaning at the individual level.

Methods: Mammograms of 39 women at elevated risk (mean age 38.7 years) who underwent 3 sequential examinations spanning the lactation period were retrospectively analyzed. Volpara-derived mammographic properties, including breast volume, fibroglandular tissue volume, volumetric breast density, compression force, and radiation dose, were automatically extracted and were statistically compared between the periods.

Results: Significant longitudinal changes in breast tissue were observed. During lactation, breast volume increased by 45%, fibroglandular tissue volume increased by 138.5%, and volumetric breast density increased by 53.2% compared with prepregnancy levels (P <.001 for all). After weaning, these values decreased by 23.3%, 52.8%, and 27.3%, respectively, compared with lactation (P <.001 for all). Breast compression was decreased by 22.3% on average during lactation compared with prepregnancy (P <.001), while it was not different between lactation and postweaning (P = .11). The radiation dose during lactation increased by 20% compared with both prepregnancy (P = .004) and postweaning (P = .005).

Conclusion: The temporal changes in mammographic properties from prepregnancy to lactation include significant increases in breast volume, fibroglandular tissue volume, breast density, and radiation dose, along with a decrease in compression force. While these changes reverse from lactation to postweaning, they generally do not return to prepregnancy levels.