There were too few tumours that were ER-ve to conduct analyses by ER status (Table 1), but results for HER-2 + ve (n = 187) and − ve (n = 1376) tumours separately each gave similar results, with statistically significantly raised risks for male infertility (p = 0.04 and 0.01, respectively) and for having no children (p = 0.01 and < 0.001, respectively) (not in Table). This evidence concerns the gene ERBB2 and male infertility.