Effect of anti-smoking health education on infant size at birth: a randomized controlled trial

Abstract

The effects of anti-smoking health education during pregnancy on smoking behaviour and the subsequent infant's size at birth were investigated in a controlled trial. It was found that the planned educational intervention was incompletely carried out and was given more effectively to primigravidae in whom subsequent reduction of smoking was more evident. The effects of educative intervention on size at birth were therefore analysed for first and later pregnancies separately. The differences in birthweight and length between the intervention and control groups were concentrated almost entirely among the first born infants who were 68 g heavier and 0.75 cm longer in the intervention group than the first born infants in the control group.

PIP: The results of a supplementary antismoking health education program targeted at women attending a prenatal clinic indicate that such efforts can be effective both in altering smoking behavior and in increasing infant size at birth. The 493 study subjects received specific advice to stop smoking as well as information about the effects of cigarette smoking on the fetus; 489 pregnant smokers registered at the same maternity clinic served as controls. Women in the intervention group were significantly more likely to stop smoking or at least reduce cigarette consumption than controls: changes in smoking behavior were recorded in 37% of study subjects compared to only 25% of controls. These differences were most marked among primigravidae: 47% of primigravidae in the intervention group compared with 31% of those in the control group stopped or reduced smoking. Significant differences in weight at birth and length between the intervention and control groups were concentrated among 1st births. For 1st births, the corrected mean birthweight difference was +68 gm (p 0.06) and for later births it was -0.5 gm. The corrected mean length difference was +0.75 cm (p 0.01) for 1st births and only +0.29 cm for later births. There was some evidence that the antismoking intervention was incompletely carried out: 61% of the primiparous women recalled being advised to stop smoking by clinic staff compared with only 45% of the multiparae. However, this factor is not considered to account for the greater effectiveness of the antismoking intervention among primigravidae. A greater behavioral response to antismoking health education by women in their 1st pregnancy has been recorded in earlier studies.