Which of the following is considered a non-risk factor in breast cancer risk calculation?

Pregnancy history is considered a non-risk factor in calculating breast cancer risk because while it does play a role in the overall understanding of breast health, it is not directly linked to an increased risk of developing breast cancer. Research indicates that having children and the age at which a woman has her first child can influence breast cancer risk, but these factors are not as significant as others like age at first menstrual cycle, family history of breast cancer, and genetic mutations.

The age at which a woman starts menstruating, family history, and known genetic mutations such as BRCA 1 and BRCA 2 are all important risk factors that have established correlations with increased breast cancer risk. Early menstruation can extend the lifetime exposure to estrogen, which is a known contributor to breast cancer. A family history of breast cancer often suggests inherited genetic predispositions, thereby heightening risk. Genetic mutations directly affect an individual's likelihood of developing the disease due to their role in tumor suppression and DNA repair mechanisms.

This context helps clarify how pregnancy history is more nuanced and doesn't equate to the strong correlations seen with other well-documented risk factors in breast cancer.