Sex of first child and breast cancer survival in young women

Two studies have reported that young women with breast cancer face increase d risk of early mortality if their first child was male rather than female. An immunological mechanism has been suggested. We sought to confirm these results in a larger, historical cohort study of 223 parous women who were a ged <45 years at breast cancer diagnosis during 1983-1987. Subjects were id entified through the Maine Cancer Registry. Follow-up data were obtained fr om hospitals, physicians, and death certificates. Reproductive history data were obtained from the next of kin of the deceased women, birth certificat es, physicians, hospitals, and lastly, subjects. With a 7-year follow-up, m ultivariate modeling found a lower mortality risk in women with a male firs t child (hazard ratio [HR] 0.51, 95% confidence interval [CI] 0.32-0.81, lo g-rank comparison). The survival advantage remained for at least 13 years i n women with a male firstborn. Thus, previous studies were not confirmed. M ortality risk in young women with breast cancer is not increased by having borne a male first child rather than a female first child.