title: High altitude and spontaneous preterm birth.
abstract: OBJECTIVE
  To study the association between high altitude and spontaneous preterm birth.
  
  
  METHODS
  Eleven placentas from cases of high altitude (3000 m) spontaneous preterm deliveries with no clinical predisposing cause were collected in Abha, a city of southern Saudi Arabia. The placentas were examined histologically using sections stained by periodic acid-Schiff and hematoxylin-eosin. The mean percentages of villi with syncytial knots and cytotrophoblastic cells were determined.
  
  
  RESULTS
  Histology of the placenta samples showed an excessive formation of syncytial knots (45.4 +/- 13.3%) and cytotrophoblastic cells (52.7 +/- 15.2%) at terminal villi.
  
  
  CONCLUSIONS
  The enhanced formation of syncytial knots and cytotrophoblastic cells is a histological feature of placental hypoxia, which may be secondary to maternal hypoxia resulting from high altitude hypoxia. Since placental hypoxia is associated with an increased incidence of spontaneous preterm birth, we suggest that high altitude may be involved in the etiology of spontaneous preterm birth.
authors.affiliation: Department of Anatomy, Abha Medical College, Saudi Arabia.
authors.forename: K Z
authors.initials: KZ
authors.lastname: Ali
authors.forename: M E
authors.initials: ME
authors.lastname: Ali
authors.forename: M E
authors.initials: ME
authors.lastname: Khalid
mesh_terms: D000531:Altitude; D046508:Culture Techniques; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000150:complications*; D015994:Incidence; D007231:Infant, Newborn; D007752:Obstetric Labor, Premature / Q000453:epidemiology / Q000209:etiology*; D010784:Photomicrography; D010920:Placenta / Q000166:cytology / Q000473:pathology*; D011247:Pregnancy; D012307:Risk Factors; D012529:Saudi Arabia