A competing risk model of sudden infant death syndrome incidence in two US birth cohorts.

OBJECTIVES: To compare changing incidence and changing risk factors associated with sudden infant death syndrome (SIDS) in the 1989 and 1996 US birth cohorts. STUDY DESIGN: All available singleton births over 500 g from the 1989 linked birth-infant death file and the 1996 and 1997 Perinatal Mortality files were examined. A log-logistic survival model was used to explicitly account for declining competing risks among low birth weight infants. RESULTS: Controlling for maternal prenatal smoking and other confounders, SIDS incidence declined by >33% between the 2 survey years (adjusted odds ratio = 0.628 with 95% CI [0.598, 0.660]). Self-reported declines in maternal prenatal smoking were also associated with significant declines in SIDS incidence. African American infants and infants born weighing <1000 g experienced increased relative risk compared with non-Hispanic white infants born weighing >2500 g. Hispanic/Latino infants had significantly lower SIDS risk than non-Hispanic white infants in both years. Accounting for declining competing risks and other factors, relative SIDS risks among infants born between 500 and 1000 g increased over the study period. CONCLUSIONS: SIDS incidence sharply declined between 1989 and 1996. High incidence of SIDS in African Americans and increased relative SIDS risk for infants born weighing <1000 g require increased attention from clinicians and public health policy makers.

Maternal smoking and adverse birth outcomes among singletons and twins.

OBJECTIVES: This study assessed the effects of maternal smoking on birth outcomes among singletons and twins. METHODS: An algorithm was developed to link twins with their siblings in the 1995 Perinatal Mortality Data Set. A random-effects logistic regression model was then used to estimate the association between maternal smoking and several adverse outcomes for a random sample of singletons and for all twins with available maternal smoking information. RESULTS: The algorithm successfully linked sibling pairs for 91% of the twin sample. Maternal smoking was associated with a significantly increased risk of low birthweight, very low birthweight, and gestation of less than 33 weeks for both singletons and twins and with an increased risk of gestation of less than 38 weeks, infant mortality, and placental abruption for singletons. Among smokers, negative impacts on the risk of low birthweight, very low birthweight, and extreme premature delivery were significantly higher for women carrying twins. CONCLUSIONS: Some of the negative effects of smoking on low birthweight and preterm delivery are greater for twins than for singletons. Women carrying twins should be warned that smoking increases their already high risk of serious infant health problems.

Maternal substance abuse and infant health: policy options across the life course.

Maternal substance abuse is a significant contributor to infant morbidity and mortality. The setting of prenatal care has long been the focus of interventions and policies to prevent these adverse outcomes. However, substance abuse programs and policies that are designed for women who are not yet pregnant can have a significant impact upon this problem. Thus it is essential to view the female life course from a broader perspective in order to consider the full range of policy options for reducing the infant mortality and morbidity caused by maternal substance abuse. This framework also allows comparisons across and between substances and offers new directions for policy development.