This article examines how pregnancy factors such as gestation length and baby's birthweight influence the risk of breast cancer in mothers. It highlights that shorter pregnancies and higher birthweights may increase the likelihood of developing breast cancer through hormonal mechanisms. The findings underscore the importance of reproductive history in breast cancer risk assessment.

Exploring How Reproductive Factors Influence Breast Cancer Risk in Mothers

Background
Parental history, including the duration of pregnancy and age at first childbirth, plays a significant role in the likelihood of developing breast cancer. Nonetheless, the influence of other pregnancy-related elements remains unclear, with studies presenting mixed results.

Methods
Analyzing data from a sizable UK cohort of 83,451 women who experienced childbirth, researchers collected comprehensive information on pregnancy details and other potential influencing factors. The study focused on how gestation duration and the baby's birthweight relate to the mother's breast cancer risk, considering various reproductive and lifestyle factors.

Results
Women who experienced shorter pregnancies with their first child appeared to have a lower risk of premenopausal breast cancer, whereas longer pregnancies were linked to increased risk (trend p=0.03). Mothers delivering high birthweight babies (≥4500g) showed a higher risk (HR=1.53). Overall, recent pregnancy gestation and birthweight had minimal impact, with similar findings observed after adjusting for confounders.

Conclusion
This research indicates that shorter pregnancies, particularly in previous births, may increase breast cancer risk, possibly due to hormonal changes early in pregnancy. Elevated birthweight might also contribute to higher risk through hormonal pathways involving estrogen and growth factors like insulin-like growth factor.