Protective Effects from the Ischemic/Hypoxic Stress Induced by Labor in the High-Altitude Tibetan Placenta.

Labor and vaginal delivery cause acute ischemic/hypoxic insult to the placenta. Previous studies demonstrate that placentas from high altitude non-natives showed blunted responses to ischemic/hypoxic insult caused by labor and vaginal birth, and there were some differences in the ATP/ADP production ratio. We hypothesized that adapted highlanders would not have a stress response to the acute hypoxia/ischemia of labor. Tibetan laboring (n = 10) and non-laboring (n = 5) and European descendants laboring (n = 10) and non-laboring (n = 5) high-altitude placentas were analyzed using genome-wide expression array analysis. There was no evidence for ischemic/hypoxic stress in high-altitude Tibetan laboring as compared with non-laboring placentas, while there were differences in gene expression between laboring and non-laboring placentas from high-altitude European descendants. Our results provide evidence for adaptation to acute hypoxic ischemic insult caused by labor and vaginal birth in placentas in a high-altitude native Tibetan population.