RESUMEN
The relationship between pregnancy and breast cancer risk is not fully understood. Most of the literature has described this interaction in terms of the age at first pregnancy and the number of full-term pregnancies. During the prospective accrual of the "Joven & Fuerte: Program for young women with breast cancer in Mexico" cohort, a series of cases with pregnancy-associated breast cancer and a history of a short inter-pregnancy interval was identified. To date, there is a very limited number of descriptions about the interaction between a short inter-pregnancy interval and breast cancer, but none specifically regarding the association of a short inter-pregnancy interval and pregnancy-associated breast cancer. Based on findings from a prospective cohort of young Mexican breast cancer patients, we hypothesize that a short inter-pregnancy interval may increase the incidence of pregnancy-associated breast cancer, possibly by amplifying the effects of the pregnancy-associated factors involved in the development of breast cancer.