Placental villus morphology in relation to maternal hypoxia at high altitude

Pregnancy at high altitude is associated with maternal hypoxaemic hypoxia w ith resultant intervillus blood hypoxia. Maternal haemoglobin concentration and blood gases mere measured in pregnant women in two cities in Peru; Lim a at sea level (n=18) and Cerro de Pasco at 4300 metres above sea level (n= 12). Following deliver), placental sections from both groups mere examined histomorphometrically using an image analysis system. Villus diameter, vill us cross-sectional nl ea, capillary diameter, capillary cross-sectional are a and the percentage of villus cross-sectional al ea occupied by villus cap illaries mere calculated and parameters were compared between the two altit ude groups. Maternal haemoglobin concentration and maternal blood pH were s ignificantly higher, and maternal pO(2), pCO(2) and O-2 saturation were sig nificantly lower in the high altitude group compared to those at sea level. The villus vessel area as a percentage of villus cross-sectional area and capillary diameter were significantly greater in the cases from the high al titude group and villus vessel area as a percentage of the villus cross-sec tional area was significantly related to maternal pO(2) (r = - 0.7, P=0.01) , and maternal pCO(2) (r = 0.7, P=0.02), but multiple 1 egression analysis demonstrated that only PO2 remained significantly independently associated with these villus histological findings (P=0.03). Placental terminal villi from term pregnancies at high altitude show different morphological feature s from pregnancies at sea level, and these changes are primarily related to maternal pO(2). The predominant morphological alteration is an increase in villus capillary diameter and therefore of the proportion of villus cross- sectional area occupied by capillary lumens. (C) 2001 Harcourt Publishers L td