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. Conclusion: 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.