Risk factors for low birth weight to adolescent mothers

The medical records of mothers less than age 20 years who delivered infants weighing 2500 g or less (n = 112) and 2500 g or more (n = 465) were reviewed to identify factors associated with low birth weight. Of the 26 medical and sociodemographic variables examined, four entered a logistic regression model to differentiate low from normal birth weight mothers: five or fewer prenatal visits, a history of a prior low birth weight infant, illness during pregnancy, and trauma (surgery or injury) during pregnancy. The relative risks and adjusted odds ratios for low birth weight associated with these variables ranged from 1.99 to 4.31. Five or fewer visits accounted for the largest proportion of low birth weight, with an etiologic fraction of 0.43. The ability of the model to discriminate between low and normal birth weight mothers was modest; its sensitivity/specificity was 0.73/0.57 in the original sample and 0.62/0.49 in a separate validation sample (n = 329). The model clarifies the factors associated with adolescent low birth weight and suggests that intervention efforts should focus on early pregnancy identification and regular prenatal care.