The University of Cambridge study on 24,000 parents and their children found that sperm cells of teenage fathers had 30 per cent higher rates of DNA mutation - increasing the risk of birth defects - compared with those of men in their twenties.
Until now, it had been assumed that DNA mutation in germ cells increases with age, as more cells divide. Scientists said that the "unexpected" findings would force "textbooks to be rewritten" but said it was not clear why teenage male germ cells are likely to accumulate more DNA errors, which can cause inherited diseases.
Mutations that occur in germ cells – which create sperm or eggs – can cause changes affecting offspring. The study found the germ cells of adolescent boys have more than six times the rate of DNA mutations as the equivalent egg cells in adolescent girls - and that the number of mutations passed down to children of teenage fathers was higher as a result.
