Randomised controlled trial of anti-smoking advice in pregnancy.

In a randomised controlled trial intensive individual anti-smoking advice given in parallel with hospital antenatal care did not influence the outcome of pregnancy. The belief that retardation of fetal growth caused by maternal smoking occurs in late pregnancy is not well based, and the advice may not have been given in time to be effective. Other possible interpretations of the results, that maternal smoking is merely an index of some other factor that retards growth or that those counselled did not reduce their smoking sufficiently to influence outcome, cannot be excluded.