4th Edition 2026

Effects of Early Pregnancy on Aging and Its Implications for Breast Cancer Risk

Published on: Feb 05, 2026

A new study from the University of California, Santa Cruz, published in Nature Communications, suggests that an early first pregnancy may reduce breast cancer risk later in life by altering how breast tissue ages. Using a mouse model that mimics human aging and reproductive history, researchers found that pregnancy prevents the buildup of abnormal “hybrid” breast cells that emerge with age and are linked to tumor development.

In mice that had never been pregnant, aging breast tissue accumulated these confused cells, which express inflammatory signals such as IL-33 and show features associated with early cancer formation. Early pregnancy acted as a long-lasting “cellular reset,” preserving normal cell identity, reducing inflammatory signaling, and restoring balance between cell types in the mammary gland.

The findings help explain why early pregnancy offers lifelong protection against breast cancer, despite risk increasing with age, and suggest that targeting age-related cellular changes could inform future prevention strategies.

Source: https://www.universityofcalifornia.edu/news/how-early-pregnancy-impacts-aging-implications-breast-cancer-risk

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