The authors performed a prospective analysis of the value of a system for scoring the risk of preterm delivery (RPD). The RPD system predicts that approximately 10% of patients will have preterm labor and delivery. Although only one third of these patients deliver before term, they account for approximately two thirds of all preterm births. The discrimination of the RPD system is better for multigravid patients than for primigravid patients, and rescoring at 26 to 28 weeks' gestation improves the accuracy of prediction.