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The male fertility clock: male fertility reduces after 40

Photo: Wellcome Images. Creative Commons.

For men the age of 40 could be the “amber light” in reproductive life, as the age of 35 is for women. After that age fertility reduces.

There is much research to indicate that male fertility decreases with age, with greater delays in achieving pregnancy, a greater chance of miscarriage or late fetal death. We reviewed the research literature and concluded that for men the age of 40 could be the “amber light” in reproductive life, as the age of 35 is for women.

It is difficult to tell what causes this. Is there a biological change, or is it just a decrease in male sexual activity? We found a way to separate these two. We looked at the risk of failure to conceive by IVF among couples where the mother was totally infertile through bilateral tubal obstruction of the absence of tubes. This removes sexual activity as an influence on the statistics. We used data from 1,938 men in 59 French IVF centres.

We did find a drop in success rate of the IVF for men older than 40. We also found that the women over the age of 35 were at greater risk too, suggesting a change in their eggs.

Research on semen in older men shows changes, in particular aberrations in the chromosomes that could be leading to a decrease in the quantity and quality of the sperm.