['To ascertain whether advanced maternal age at birth is associated with offspring infertility.', 'A written questionnaire was completed by infertile couples attending our clinic in the presence of a researcher.', "Maternal age at birth (odds ratio 1.236, 95% CI 1.100-1.388) and birth order of all respondents and their respective siblings (odds ratio 0.551, 95% CI 0.351-0.865) were significant predictors of male infertility. The probability of a man being infertile increased as mother's age at birth increased (regression coefficient +/- standard error 0.212 +/- 0.059; P < 0.001), but decreased as birth order increased (regression coefficient +/- standard error -0.596 +/- 0.230; P = 0.010)."] Does delayed motherhood increase the probability of sons to be infertile?