Impact of Pregnancy Factors on Women's Breast Cancer Risk
This study explores how pregnancy duration and infant birthweight influence breast cancer risk. Shorter pregnancies appear to increase pre-menopausal breast cancer risk, while higher birthweight babies are associated with a higher overall risk. These insights enhance understanding of pregnancy-related cancer risks, informing future research and prevention strategies.
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Introduction
While parity and age at first childbirth are well-known influences on breast cancer risk, the effects of other pregnancy-related characteristics remain unclear with inconsistent findings across studies.
Study Overview
Involving 83,451 women from the UK general population, this study collected detailed data on each pregnancy and various potential confounders. Researchers examined how gestation length and the birthweight of offspring relate to breast cancer risk, accounting for both reproductive and non-reproductive factors, unlike prior large-scale investigations.
Key Findings
Shorter first pregnancies were associated with a lower risk of pre-menopausal breast cancer (p trend=0.03; HR for 26–31 weeks vs. 40–41 weeks=2.38, 95% CI 1.26–4.49) and showed a borderline link to overall breast cancer risk (p trend=0.05). Mothers of higher birthweight infants (≥ 4500 g) had a higher breast cancer risk (HR=1.53, 95% CI 1.06–2.21). No significant effects were observed related to gestation or birthweight from more recent pregnancies. Analyses adjusting for confounders yielded similar results.
Conclusion
Findings support the idea that shorter pregnancies may elevate pre-menopausal breast cancer risk, possibly due to hormonal effects and early breast tissue proliferation. Additionally, high birthweight infants may be linked to increased risk, potentially through estrogen and insulin-like growth factor 1 pathways.
