title: Mechanism of parturition and preterm labor.
abstract: 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.
  
  
  BACKGROUND
  Gynecologists and Family Physicians
  
  
  OBJECTIVE
  After completion of this article, the reader will be able to describe potential mechanisms of partition and preterm labor and to list the various substances that can inhibit and promote myometrial contractions.
authors.affiliation: Department of Physiology, University of Toronto, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Ontario, Canada. j.challis@utoronto.ca
authors.lastname: Challis JRG
mesh_terms: D000328:Adult; D005260:Female; D005938:Glucocorticoids / Q000009:adverse effects; D006801:Humans; D007743:Labor, Obstetric / Q000502:physiology*; D009215:Myometrium / Q000502:physiology; D007752:Obstetric Labor, Premature / Q000209:etiology* / Q000503:physiopathology / Q000628:therapy; D011247:Pregnancy; D011453:Prostaglandins / Q000494:pharmacology*; D012307:Risk Factors; D014590:Uterine Contraction / Q000502:physiology*; D014599:Uterus / Q000502:physiology*
chemical_list: D005938:Glucocorticoids; D011453:Prostaglandins