Women who give up smoking during pregnancy are more likely to have easygoing children than those who smoke, new research suggests.

Past studies have shown that pregnant women who smoke have a higher risk of miscarriage, premature labour and children with low birth weight.

Latest research from scientists at the University of York now says smoking also affects offspring's personality.

They studied over 18,000 UK babies born between 2000 and 2002 and determined whether their mothers were smokers.

Mothers were classified as non-smokers, quitters, light smokers, or heavy smokers (ten or more cigarettes a day).

The researchers assessed infants at nine months old, gauging their temperaments including positive mood, receptivity to new things and regular sleep and eating patterns in infants.

Writing in the Journal Of Epidemiology and Community Health, the researchers say that mums-to-be who quit smoking had the most easygoing infants, compared with non-smokers and smokers.

Their children had the lowest chances of unpredictable behaviour and of becoming distressed when faced with new situations.

In comparison, heavy smokers had the most difficult children with the least positive mood.

The researchers say smoking during pregnancy passes on harmful chemicals to the unborn offspring, affecting personality and behaviours.

"The trend of an association of heavy smoking with infant difficult mood adds weight to the burgeoning evidence that pregnancy smoking may have [a causal] role in the development of problem behaviours," the researchers conclude.

"Most notably, the present findings converge with other recent studies using a variety of methods and designs, which demonstrate that atypical behavioural patterns in the offspring of persistent pregnancy smokers are evident as early as the first years of life."

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