Smoking, intra-uterine growth retardation and sudden infant death syndrome

Background Sudden infant death syndrome (SIDS) is associated with factors such as maternalsmoking and low birthweight, which may be linked causally. Recent pathologicalstudies have shown evidence for growth retardation at organ level in SIDS infantswhose weights at birth were above the tenth centile, and were not thereforerecognized as growth retarded clinically. It might be of value to identify such hiddengrowth retardation at birth, and to have an estimate of how much of it may beassociated with maternal cigarette smoking.Methods 104 SIDS victims who died between 1987 and 1992 and who were brought to asingle children's hospital, were compared to 206 controls, matched for place anddate of birth. Birthweight, occipitofrontal head circumference, maternal age, andsmoking habit, and height and weight at booking were recorded. Birthweightratio (BWR), head circumference ratio (OFCR), and a growth retardation ratio(GRR = OFCR/BWR) were computed for each infant.Results No significant differences were seen between SIDS and control groups for BWR,OFCR or GRR. Separating smoking mothers from non-smokers in both groupsshowed significant growth retardation in smokers' children. SIDS infants of non-smokers as a group were not growth retarded, but had a lower gestational ageat birth. Logistic regression analysis showed SIDS to be significantly related togestation (OR 0.86/week) and smoking (OR 4.8), but not independently to BWR,maternal age or maternal body mass index (MBMJ).Conclusion Most of the risk of SIDS associated with growth retardation may be accounted forby maternal smoking.Keywords Smoking, sudden infant death syndrome, intra-uterine growth retardationAccepted 18 August 1997Despite a recent welcome reduction in the incidence of suddeninfant death syndrome (SIDS), it remains a major cause of post-neonatal mortality in Western countries. Many demographicand environmental variables have been shown to be associatedwith an increased risk of SIDS both in univariate analyses andin logistic regression models, after adjusting for confoundingvariables.Maternal cigarette smoking both antenatally and postnatallyhas been associated with an increased risk of SIDS, although thecausative mechanism, if any, is unclear.