People who are born small have less chance of climbing the career ladder later in life, according to researchers.

A study of more than 14,000 children born in the UK in 1970 found that those born underweight were less successful academically and less likely to become professionals or managers than people born at a normal weight.

The study, by Dr Richard Strauss at the department of paediatrics, University of Medicine and Dentistry in New Jersey, USA, measured years of education, occupation, income, marital status, life satisfaction and height of a group of 26-year-olds.

Professional or managerial

Just 9% of people born small had professional or managerial jobs, compared with 16% of those showing normal weight as babies. Their weekly income was also significantly lower - �185, as opposed to �206.

And the adults who started life smaller, remained so, being 5cm shorter on average.

Taking into account small head size of babies gave even more significant results - of people with low birth weights and with small heads at the age of five, only 3% went on to become professionals or managers.

Dr Strauss said in the Journal of American Medical Association: "Those born small for gestational age (SGA) have increased academic difficulties persisting into adolescence. As young adults, those born SGA also have deficits in professional and economic attainment."

But he added: "Solely focusing on neurodevelopmental testing ignores the social and emotional outcome of adolescents and adults who were SGA, which appears to be excellent."

Satisfied with life

Professor Sally McGregor at the Institute of Child Health, in London, said: "This area is a bit murky at the moment."

Although studies have been carried out into premature babies, little work has been done on the effect of being born at full-term with a low weight, and results are contradictory, she said.

The number of low birth babies was lower now than in the 1970s and better care was available, added Professor McGregor, who is carrying out a similar study on babies in Jamaica.

She welcomed the finding that the birth babies turned out to be equally happy in adult life, saying this went against established thinking that they "did not do so well".

"It is not surprising that they are a little bit behind, what is surprising is that they are satisfied with life."