Incidence of preterm delivery in patients with previous preterm delivery and/or abortion.

Patients with a history of two or more pregnancies which ended spontaneously before 37 weeks' gestation had an increased risk of spontaneous labour and delivery in subsequent pregnancies. This risk was correlated with previous second trimester abortion and spontaneous preterm delivery but not with previous first trimester abortions. Patients with one or more pregnancies ending in spontaneous second trimester abortion or with preterm labour and delivery had a 38--43% risk of again delivering before term.