Maternal smoking: an increasing unique risk factor for sudden infant death syndrome in Sweden

To assess the change of risk factors that are specific to sudden infant death syndrome (SIDS) after the initialization of a campaign to reduce the risk (RTR) of SIDS compared to non-SIDS postneonatal deaths.

Data were extracted from the Swedish Medical Birth Registry, 1982-1991 and 1993-1998. 1105 infants died from SIDS during the postneonatal period. 2115 postneonatal deaths were from other causes and 11,050 live birth controls were selected. Risk factors previously identified to be related to SIDS were defined as high parity, prematurity, young maternal age, low Apgar score, birth during the night, single motherhood, multiple births, maternal smoking, male gender, short length standard deviation score (SDS) and small weight-to-length SDS.

Non-SIDS deaths were more significantly related to a low 5-min Apgar score, smaller weight-to-length SDS, and/or short length SDS values; while SIDS deaths were more closely related to mothers with higher parity or multiple births, mothers who smoked during pregnancy and single-parent (mother) families. Maternal smoking was even more prominent among SIDS deaths in the post-campaign period. The adjusted odds ratios, compared with non-SIDS deaths, increased from 1.84 (95% CI: 1.48, 2.28) in the pre-campaign period to 4.11 (95% CI: 2.72, 6.21) in the post-campaign period.

Maternal smoking during pregnancy remains the most important modifiable risk factor for SIDS in the post-campaign period in comparison with non-SIDS postneonatal deaths. Other than putting babies in a supine sleeping position, maternal smoking should be the next most important issue to be considered, if there is to be a second campaign.