Men have biological clocks too
According to a new study, all sperm is not created equal: male gametes weaken with age.
Scientists say they have found more evidence that men as well as women have biological clocks and that they start to tick in their mid-30s.
A French study of over 12,200 couples having fertility treatment suggests the chance of a successful pregnancy falls when the man is aged over 35.
It adds that the chance is significantly lower if he is over 40.
Previous studies have shown that both natural and assisted conception is more difficult if the man is over 40.
The researchers told a European reproductive health conference that it was likely the problems were caused by DNA damage in sperm.
As expected, maternal age had an effect in women over 35, who had a significantly higher chance of miscarriage and lower rate of pregnancy.
But the team also found that, where the father was in his late 30s, miscarriages were more common than if the man was younger.
And if a man was over 40, the chances of a successful pregnancy were even lower.
For those couples, a third of pregnancies ended in miscarriage and only 10% of treatments resulted in pregnancies.
Jacques de Mouzon, of the French National Institute for Medical Research, another member of the study team, said: “People say men are fertile into old age, 90 even. That may be true sometimes, but the product is different. There is a decrease for men in fertility and an increase in the spontaneous abortion rate. It is necessary for men to try to have children before the ages of 40 to 45.”