Preterm delivery is the chief problem in obstetrics today, accounting for 70 percent of perinatal mortality and nearly half of long-term neurologic morbidity.¹,² Approximately 10 percent of all births are preterm, but most of the serious illness and death is concentrated in the 1 to 2 percent of infants who are born at less than 32 weeks of gestation and who weigh less than 1500 g. Approximately 20 percent of preterm births are the result of a physician's decision to bring about delivery for maternal or fetal indications, and the remainder follow the spontaneous onset of labor or rupture . . .