A new study provides more evidence that sons of women who underwent fertility treatment may be more likely to have fertility problems themselves.

Earlier this year, Danish researchers were the first to report a link between infertility treatment of mothers and poor semen quality in male offspring.

But Dr. Cecilia Host Ramlau-Hansen of Aarhus University Hospital in Aarhus, Denmark and colleagues say it’s possible that maternal obesity may have been a factor in the relationship, given that heavier women are more likely to be infertile and tend to have higher estrogen levels, which could effect the development of male sex organs in the womb. Sperm-damaging pollutants are also known to collect in fatty tissue.

To investigate the role of obesity, Ramlau-Hansen and colleagues, who were not involved in the original study, analyzed data from a study of maternal smoking in pregnancy and sons’ semen quality. Among the 325 men aged 18 to 21 participating in the study, 30 had mothers who reported having been “examined or treated for childlessness.”

They found that the young men whose mothers had fertility problems had lower sperm counts, lower sperm concentrations, fewer normally formed sperm, and worse sperm motility. None of the differences, except for sperm concentration, were statistically significant, but this may have been due to the small size of the study.

The body mass index (BMI) of the mothers, a measurement of weight in relation to height, did not appear to play a role in the relationship between infertility and low sperm count, Ramlau-Hansen and her colleagues say.

“It is unknown whether the poor semen quality is related to infertility treatment or is caused by male or female infertility itself, for instance, through hereditary factors,” they write.

“It is important,” they conclude, “to get data that can address this issue, since it is plausible that some infertility treatments may impact [organ development] and function of the testis.”

SOURCE: American Journal of Epidemiology, September 1, 2007.