O2 delivery to the pregnant uterus: its relationship to O2 consumption

Normal sheep were studied at intervals of 3-5 days during the last weeks of pregnancy in order to evaluate variability in rate of O2 consumption (QO2) of the uterus in relation to several variables involved in delivery of O2 to the organ. Among-animal differences of uterine QO2 were statistically significant and directly related to birthweight of the lamb. Among-animal differences of uterine blood flow (UBF) and uterine arteriovenous O2 content difference [C(a-v)O2] also were statistically significant, though neither was related to birthweight, presumably since they tended to vary inversely with one another. In a given ewe relative magnitude of UBF and of C(a-v)O2 was related to maternal arterial O2 content (CaO2), day of pregnancy, and whether the animal carried singlets or twins. Variability in QO2 was most closely related to UBF, although its relations to C(a-v)O2 and CaO2 were significant also. These data suggest there are systematic relationships among variables involved in the delivery of O2 to the uterus of pregnant sheep.