Objective: The objectives of this study were to 1). study the incidence of sudden infant death syndrome (SIDS) among singleton births in the United States and 2). identify maternal and obstetric risk factors for SIDS.
Methods: A cohort of all live births in the United States from 1995 to 1998, formed the source population (n = 15627404). The data were obtained from the National Centers for Health Statistics Linked Births and Infant Deaths File. A nested case-control study was used to examine risk factors for SIDS. From this birth cohort, all SIDS deaths (n = 12404) were first identified (case group). From the remaining non-SIDS births, a 4-fold larger sample (n = 49616) was randomly selected as a control group.
Results: The overall incidence of SIDS was 81.7 per 100000 live births. More mothers in the case group than in the control group were reported to have placenta previa (odds ratio [OR]: 1.70; 95% confidence interval [CI] 1.24, 2.33), abruptio placentae (OR 1.57; 95% CI 1.24, 1.98), premature rupture of membranes (OR 1.48; 95% CI 1.33, 1.66), or small for gestational age (OR 1.40; 95% CI 1.30, 1.50 for the 10th percentile). SIDS cases were also more likely to be male. Mothers of cases were more likely to be younger, less educated, and nonwhite, and more of them smoked during pregnancy and did not attend prenatal care.
Conclusion: This analysis confirms the importance of several well known demographic and lifestyle risk factors for SIDS. In addition, placental abnormalities were risk factors for SIDS.
Level of evidence: II-2