Increased incidence of placental chorioangioma in high-altitude pregnancies: Hypobaric hypoxia as a possible etiologic factor

OBJECTIVES: Our purpose was to determine the effects of pregnancy at high altitude on the human placental structure. STUDY DESIGN: Histologic material from 22 term placentas delivered at altitudes above 3600 m was examined and compared with control material from 760 m. RESULTS: Intraplacental chorioangiomas were identified in 5 of the 22 high-altitude placentas but in none of the 59 controls. The lesions were not visible on the external surface of the placentas and were not encapsulated. The state of differentiation varied; some contained numerous capillaries that showed sinusoidal dilations, whereas in others at the opposite extreme mesenchymal cells predominated. The presence of chorioangiomas was frequently associated with threatened premature delivery, a circumvallate placenta, and multiple infarction. The lesions represented only a small percentage of the overall placental volume (<10%). CONCLUSIONS: The increased incidence of placental chorioangioma observed at high altitude (above 3600 m) may be due to the prevailing hypobaric hypoxia. Overexpression of angiogenic cytokines such as vascular endothelial growth factor, which is known to be up-regulated by this factor in vitro, may mediate this effect.