Fertility problems may be partially inherited

Young men whose parents had difficulty conceiving are likely to have relatively poor sperm quality, a new study shows - offering evidence that fertility problems are at least partly inherited in some cases.

The study, of 311 Danish men ages 18 to 21, found that those whose parents took longer than one year to conceive tended to have a lower sperm count and fewer normal-looking sperm.

The findings are consistent with the notion that fertility problems have at least some heritable causes, lead researcher Dr. Cecilia H. Ramlau-Hansen told Reuters Health.

She and her colleagues at Aarhus University Hospital in Denmark report the findings in the American Journal of Epidemiology.

Genes play an important role in sperm development, but the extent to which heredity contributes to male infertility is not clear. Some studies have found poorer sperm quality in men whose mothers had undergone infertility treatment; however, it is not known whether this reflects heredity or effects of the treatment itself.

The new study included only young men whose parents conceived without fertility treatment.

Ramlau-Hansen and her colleagues analyzed semen samples from 311 young men whose mothers had taken part in a healthy-pregnancy study in the 1980s. In most cases, the men's parents had taken 6 months or less to conceive, but 11 percent were born to parents classified as subfertile as they took more than a year to get pregnant.

The researchers found that men with subfertile parents had a 22 percent lower sperm concentration and a smaller percentage of structurally normal sperm than men born to parents of normal fertility.

Because of the study design, it's not possible to tell whether the poorer sperm quality might be related to inherited factors from the father, mother or both, Ramlau-Hansen said.

If impaired fertility is passed on from parents, she and her colleagues note, it's possible that fertility problems could become more common as more and more infertile couples conceive with the help of assisted reproduction.

"Genes responsible for impaired sperm production would normally be eliminated by evolution," the researchers point out, "but assisted reproduction technology interferes with this force of selection, and the long-term consequences are not known."

However, they also acknowledge that the findings are based on a small number of men, and further research is needed to confirm the results.

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SOURCE: American Journal of Epidemiology, June 15, 2008.

By Amy Norton
NEW YORK (Reuters Health)