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

Background Sudden infant death syndrome (SIDS) is associated with factors such as maternal smoking and low birthweight, which may be linked causally. Recent pathological studies have shown evidence for growth retardation at organ level in SIDS infants whose weights at birth were above the tenth centile, and were not therefore recognized as growth retarded clinically. It might be of value to identify such hidden growth retardation at birth, and to have an estimate of how much of it may be associated with maternal cigarette smoking. Methods 104 SIDS victims who died between 1987 and 1992 and who were brought to a single children's hospital, were compared to 206 controls, matched for place and date of birth. Birthweight, occipitofrontal head circumference, maternal age, and smoking habit, and height and weight at booking were recorded. Birthweight ratio (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 groups showed significant growth retardation in smokers' children. SIDS infants of nonsmokers as a group were not growth retarded, but had a lower gestational age at birth. Logistic regression analysis showed SIDS to be significantly related to gestation (OR 0.86/week) and smoking (OR 4.8), bur not independently to BWR, maternal age or maternal body mass index (MBMI). Conclusion Most of the risk of SIDS associated with growth retardation may be accounted for by maternal smoking.