Parental Smoking and Sudden Infant Death Syndrome: A Review of the Evidence

This paper reviews evidence relating parental smoking to sudden infant death syndrome (SIDS) risk in their offspring, based on English-language papers covering the period 1966–1996. Twenty-eight prospective and case-control studies provided suitable data. The studies mainly considered maternal smoking during pregnancy, but some studies provided data for maternal smoking before pregnancy, at the time of conception or postnatally, for paternal smoking at various times and/or for postnatal smoking by other household members and day-care providers. Tables were constructed listing unadjusted and covariate-adjusted relative risk estimates for each index of exposure. Associations between SIDS and maternal smoking both during and after pregnancy were consistently observed. Relationships with paternal smoking and with other sources of exposure were also reported in a number of studies. Dose-response relationships were seen for various exposure indices. Several studies found that adjustment for numerous potential confounders very substantially weakened the association between SIDS and parental smoking. Although the possibility of a causal explanation of the associations observed cannot be excluded, the existence of various study weaknesses and the likelihood of residual confounding means that one cannot infer with confidence that parental smoking actually does increase the risk of SIDS.