Sudden infant death syndrome among extremely preterm infants: United States 1997-1999

Background: Preterm infants have been reported to be at higher risk than term infants for sudden infant death syndrome (SIDS). Reasons for this higher risk are not clear. Ojective: The objective of this study was to analyze medical and demographic characteristics among infants 24 to 32 weeks gestation to identify characteristics more prevalent among infants dying of SIDS in the postneonatal period than among infants of similar gestation who survived of who died of other causes in the postneonatal period. Design/Methods: United States linked birth and death certificate period data for 1997 to 1999 were used for this analysis. The population used was limited to infants 24 to 32 weeks gestation weighing 500 to 2500 g. SIDS deaths were limited to the postneonatal period and compared to survivors and infants dying in the postneonatal period of other causes. Results: There were 469 postneonatal SIDS deaths with complete data (rate=2.2/1000 live births surviving ≥ 28 days); 3950 other postneonatal deaths (rate = 18.7/1000) and 206,640 survivors. Compared with survivors, infants dying of SIDS were more likely to be born to mothers with <12 years of education (odds ratio = 2.5, 95% confidence interval (95% CI = 1.8, 3.3); be born to mothers ≤17 years of age (OR = 2.0, 95% CI = 1.4, 2.8); and be born to mothers with >3 pregnancies (OR = 2.6, 95%, CI = 1.9, 3.5). Compared with infants dying in the postneonatal period of other causes, these same demographic factors continued to be significant risk factors for SIDS. The were no medical risk factors such as breech presentation, abruptio placenta, Apgar score <4 at 5 minutes, or mechanical ventilation for >30 minutes after birth, for which infants dying of SIDS were at greater risk than survivors or infants dying of other causes. Conclusions: Risk factors for SIDS among infants 24 to 32 weeks gestation appear to be more associated with sociodemographic characteristics than medical characteristics. This suggest that for the immediate future, the risk for SIDS among very preterm infants will be best addressed through further modification of the environment and parent behavior.