Preterm birth occurs in 5 to 10 percent of all pregnancies and accounts for 75 percent of neonatal mortality and morbidity, including long-term handicap. Thirty percent of preterm birth may be associated with an underlying infective process, and approximately 50 percent are idiopathic. Preterm birth corresponds to a syndrome with a variety of causes. The factors contributing to preterm birth may vary at different “windows” of gestation. Glucocorticoids seem to have a central role in processes of birth at term and preterm, and alter synthesis and/or activity of key enzymes in prostaglandin synthesis and metabolism as well as increasing corticotropin-releasing hormone output by intrauterine tissues. This new information should facilitate development of improved methods of diagnosis and therapy for patients at risk of preterm labor.