Hematologic evidence of fetal hypoxia among newborn infants at high altitude in Bolivia.

The reduced birth weight widely reported for high-altitude infants has been attributed to intrauterine hypoxia. This assertion may be tested by comparing hematologic values of high-altitude and low-altitude newborn infants, since the human fetus can respond to intrauterine hypoxia with enhanced erythropoiesis. This report presents cord blood values of term Bolivian infants classified by altitude, ethnic group, and parity: 105 from La Paz (3600 m) and 46 from Santa Cruz (400 m). Hematocrit, hemoglobin concentration, and the proportion of hemoglobin F are higher among newborn infants at high altitude. Ethnic group and parity interact with altitude in effect on hematocrit and hemoglobin concentration. Gestational age, birth weight, maternal hematologic variables, and socioeconomic indicators are not significantly associated with cord blood values. The high-altitude newborn infant displays evidence of enhanced erythropoiesis, which supports the suggestion that the high-altitude fetus experiences a greater degree of hypoxia in utero than does the low-altitude fetus.