Pregnant teenagers are in better physical condition, suffer from fewer chronic diseases, and engage in fewer health-risky behaviors than socioeconomically similar pregnant adults, but give birth to a disproportionately large number of preterm infants. This systematic review of the adolescent pregnancy literature defines the unique risks associated with being young and pregnant by examining how the physical and psychosocial changes that are characteristic of puberty and adolescence interact with traditional risk factors for preterm delivery. The need for age-specific interventions is discussed and recommendations for future research are made.