In this study, perinatal data from 73 children with sudden infant death syndrome (SIDS) and 73 matched controls were compared. Birthweight, length and circumference of the head were significantly smaller in cases of SIDS. The odds ratio for SIDS when mothers who had smoked 1-10 cigarettes per day were compared with non-smokers was 2.3 (95% confidence interval: 1.0-5.7). The odds ratio was 6.2 (95% confidence interval: 2.8-14.1) when the mother had smoked more than ten cigarettes daily during pregnancy. Approximately 40% of all pregnant women still smoke during pregnancy. The challenge is to pass on this information in a proper way in order to reduce/stop smoking during pregnancy.