Jensen et al. (Am J Epidemiol 2007;165:583–90) reported for the first time that men whose mothers had received fertility treatment had poor semen quality. This result could be confounded by the mothers' body mass index. Obesity is a strong predictor of fecundity and could have a programming effect on semen quality through hormonal factors or links to fetal growth. The authors of the current study tried to replicate the finding of Jensen et al. after controlling for maternal body mass index and other covariates using data from a recently conducted, population-based, Danish follow-up study on the association between maternal smoking during pregnancy in 1984–1987 and sons' semen quality, in which the participants were sampled according to levels of maternal smoking during pregnancy. After adjustment, sons of mothers who reported that they had been examined or treated for childlessness (n = 30) had a lower sperm concentration and total sperm count and fewer motile and morphologically normal spermatozoa in comparison with sons of mothers who had not been examined or treated for childlessness (n = 295). None of the differences (except for semen concentration) between the groups reached statistical significance, but the study has limited power. The findings were in the same direction as those reported by Jensen et al. and do not indicate that their results are confounded by maternal body mass index.