Diminishing returns

Age hits hopes of fatherhood

Men should not assume they will become fathers in later life, as fertility declines with age, scientists have warned.

Research has revealed how sperm reduces in quality as men grow older.

A study of 527 couples in Boston found that embryos created with sperm from men over the age of 50 grow 35 per cent more slowly compared with men in their mid-30s.

And a team in New York tested different age groups and showed that fertilisation rates declined from 87.7 per cent to 46 per cent with age.