OBSERVATIONS ON THE PLACENTAL EXCHANGE OF THE RESPIRATORY GASES IN PREGNANT EWES AT HIGH ALTITUDE

Abstract

The oxygen and carbon dioxide contents and tensions have been determined in the maternal arterial, uterine venous, umbilical arterial and umbilical venous bloods respectively, at selected stages in gestation in a series of pregnant sheep bred and pastured at high altitude— circa 14,000–15,000 ft.—in the Peruvian Andes. The results demonstrate that despite the lowered oxygen tension in the maternal uterine, and presumably in the maternal placental capillaries, the oxygen tension in the umbilical vessels is similar to that reported for fetuses carried by ewes at sea level. The probable mechanisms through which the fetus carried by a ewe at altitude obtains an adequate oxygen supply from the maternal blood despite the lowered tension in that source are discussed.