Predicting the risk for sudden infant death syndrome from obstetric characteristics: A retrospective cohort study of 505 011 live births

OBJECTIVE. We sought to develop a simple robust method for assessing the risk for sudden infant death syndrome (SIDS) on the basis of obstetric characteristics. METHODS. A population-based retrospective cohort study was conducted of data from the linked Scottish Morbidity Record, Stillbirth and Infant Death Enquiry and General Registrar's Office database of births and deaths, encompassing births in Scotland between 1992 and 2001. All women who had a singleton live birth between 24 and 43 weeks' gestation and for whom data were available (n = 505 011), divided into model development and validation samples, were studied. The main outcome measure was death of the infant in the first year of life as a result of SIDS. RESULTS. The risk for SIDS was modeled in the development sample using logistic regression with the following predictors: maternal age, parity, marital status, smoking, and the birth weight and the gender of the infant. When the model was evaluated in the validation sample, the area under the receiver operating characteristic curve was 0.84 and the incidence of SIDS was 0.7 per 10 000 (95% confidence interval: 0.3-1.4) among 126 253 women in the lower 50% of predicted risk and 29.7 per 10 000 (95% confidence interval: 23.4-37.2) among the 25 250 women in the top 10% of predicted risk. A logistic-regression model then was developed for the whole population, and the output was converted into adjusted likelihood ratios. These are tabulated and provide a simple method for assessing the risk for SIDS associated with any combination of obstetric characteristics. CONCLUSIONS. A model that uses maternal characteristics and outcome at birth is predictive of the risk for SIDS. This model is presented in a simple form that allows calculation of the individual risk for SIDS.