Pregnancy at High Altitude: A Hyperviscosity State.

摘要

In nonpregnant subjects, the state of hypobaric hypoxia existing at high altitude is associated with increased erythropoiesis and reduced total body water, leading inevitably to hyperviscosity. Hyperviscosity in women at altitude has been linked with intrauterine growth restriction and preeclampsia. This cross-sectional study enrolled 94 women having singleton pregnancies who lived 4370 meters above sea level. They were evaluated when coming for routine antenatal care at 10 to 38 weeks gestation, along with 75 women living at sea level. Nonpregnant control women included 24 living at altitude and 17 at sea level.In nonpregnant control women, blood viscosity was higher at high altitude. In pregnant women, whether at sea level or high altitude, blood viscosity declined as gestation advanced but was significantly higher at altitude than at sea level. Hematocrit also decreased during gestation; levels were higher at altitude. At high altitude, hematocrit levels were higher in pregnant than in nonpregnant control women. Plasma viscosity decreased during gestation in pregnant women at sea level but did not change in the high-altitude group. Total protein levels decreased as gestation proceeded in both groups of pregnant women but were higher in the high-altitude group. At altitude, total protein levels were lower in pregnant women. Fibrinogen levels were higher at altitude than at sea level. In pregnant women at sea level, concentrations increased with gestation. At altitude, fibrinogen levels were similar in pregnant and nonpregnant women. Albumin concentrations decreased with gestation both at sea level and at high altitude. Levels were lower at high altitude than at sea level in pregnant women. At altitude, albumin levels were lower in pregnant women than in the nonpregnant control women.This study demonstrates that, in pregnant women living at high altitude, blood viscosity is increased as a result of increases in hematocrit and plasma viscosity. The result may be increased resistance to blood flow in the placental bed, which has a sensitive low-shear circulation. Whether hyperviscosity affects fetal and maternal adaptation during pregnancy at high altitude remains to be determined.