Effects at age nine of maternal smoking in pregnancy: experimental and observational findings

Objectives Fo compare long term outcomes of a randomised controlled trial o f anti-smoking education in pregnancy and to examine the same outcomes acco rding to maternal pregnancy smoking behaviour. Design Follow up of the population included in the randomised controlled tr ial nine years later and of ex-smokers and non-smokers within the same hosp ital population. Setting A maternity hospital in Birmingham with follow up of children in sc hools and mothers at home. Population 1218 smokers recruited to the trial; also 191 ex-smokers at hook ing and 414 non-smokers through out pregnancy. Methods Children were assessed individually by psychologists in schools, an d mothers interviewed at home to obtain additional information relevant to cognitive development and growth. Information on smoking during pregnancy w as obtained from mothers and obstetric data from computerised case-notes, b oth recorded immediately following delivery. Main outcome measures Height, weight, IQ and neurological soft signs at 9.4 years. Results Differences in birthweight and length between the intervention and control groups were confirmed but no intervention-control differences were found at age 9.4 fur weight? height, IC! or neurological soft signs. Differ ences were found for height and IQ according to mothers pregnancy smoking b ehaviour, but smoking diet not remain an independent predictor after taking account of confounding factors. Alternative classifications of smoking beh aviour, taking account of the gestation at stopping and mean cigarette cons umption throughout pregnancy likewise showed no effect. Conclusions The well established early hazards of smoking during pregnancy seem to be resolved by later childhood, with no evidence of direct long ter m effects on growth or cognitive functioning.