Remodelling of uteroplacental arteries is decreased in high altitude placentae.

Uterine blood flow and birth weight are reduced and the risk of pre-eclampsia is increased in high-altitude pregnancies. Since IUGR and pre-eclampsia are associated with reduced invasion and remodelling of maternal spiral arteries we asked whether the terminal ends of uteroplacental arteries located at the maternal-foetal decidual interface evidenced less remodelling in 19 high (3100 m) compared with 13 moderate (1600 m) altitude placentae from normal pregnancies. Previous work has demonstrated marked villous angiogenesis in high altitude placentae. We asked whether such changes are compensatory for reduced modelling and/or whether they contribute to increased birth weight. Placentae were randomly sampled and examined with immunohistochemistry to evaluate vessel remodelling and foetal capillary density. The decidual ends of uteroplacental arteries were 8-fold more likely to be remodelled at 1600 vs. 3100 m (OR=8.1; CI 2.4, 27.0,P< 0.001). There were more than twice as many uteroplacental arteries observed in the high vs. moderate altitude placentae (OR=2.1; CI: 1.3, 3.5, P=0.006). Foetal capillary density was greater at 3100 vs. 1600 m (P< 0.001), but did not relate to remodelling nor to birth weight. In this in vivo model for chronic hypoxia, remodelling is reduced, and villous angiogenesis is not fully compensatory for reduced PO(2).