'Stop smoking in pregnancy for more relaxed babies'

Women who give up smoking in pregnancy have more relaxed children, research suggests. At nine months, children of women who quit while pregnant were more positive, more receptive to new things and more likely to have regular sleeping and eating patterns.

The findings are based on 18,000 babies born between 2000 and 2002 who took part in the Millennium Cohort Study.

The beneficial effect of quitting appears to come from a combination of avoidance of the toxic effects of smoke on the foetus and an improvement in the caring ability of the mother.

The results, published in the Journal of Epidemiology and Community Health, showed mothers who gave up smoking had the most easygoing infants, compared with those of both smokers and non-smokers.

Heavy smokers had the most difficult children, with the lowest scores for positive mood. Previous animal research has shown that nicotine is a behavioural toxin.

Pregnant smokers may also have behaviour associated with continuing to smoke that affects their children's development.

Giving up smoking in pregnancy is associated with an urge to protect the baby, the researchers from the University of York say. This is different from efforts to quit long term, as relapse rates are high after birth.

Giving up may show the capacity to adapt to circumstances and the ability to delay gratification absent in women who keep smoking.