Smoking during pregnancy and poor antenatal care: two major preventable risk factors for sudden infant death syndrome.

BACKGROUND In this case-control study on sudden infant death syndrome (SIDS), the magnitude of the risk factors 'maternal smoking during pregnancy' and 'poor antenatal care' was assessed and the attributable proportions of SIDS incidence estimated. METHODS Perinatal data from 190 SIDS cases, who died between 1986 and 1990 at age > 7 days and had a diagnosis of SIDS confirmed by autopsy, were compared to 5920 controls. Adjusted odds ratios (OR) and 95% confidence intervals (CI) were computed by unconditional logistic regression. The attributable risk per cent among the exposed (AR%) and the population attributable risk per cent (PAR%) were calculated. RESULTS Maternal smoking during pregnancy was associated with a more than twofold risk of SIDS (OR = 2.4; 95% CI: 1.7-3.4) and showed a significant dose-response. Low numbers of antenatal care visits were also associated with an increased risk of SIDS: OR = 1.6 (95% CI: 1.1-2.3) for 4.8 consultations and 2.9 (95% CI: 1.4-5.8) for 0-3 consultations; reference: > 8 consultations. Maternal smoking during pregnancy yielded an AR% of 58% (95% CI: 42-70) and a PAR% of 28% (95% CI: 16-40). The AR% for < or = 8 antenatal care visits versus > 8 consultations was 41% (95% CI: 16-59); the PAR% 10% (95% CI: 3-17). CONCLUSIONS Assuming causality, our data suggest that a reduction of the prevalence of either risk factor by population-based interventions may yield a worthwhile public health impact in terms of a substantially lower SIDS incidence.