The flow resistance of the maternal placental vascular bed of anesthetized guinea pigs.

In anesthetized guinea pigs, the maternal placental vascular bed (the spiral arteries and the trophoblastic lacunae with the draining veins) was perfused with blood via a tube connecting a carotid artery and a spiral artery. The placental blood flow and the blood pressures at the beginning of the perfused spiral artery, in the peripheral part of a nonperfused spiral artery and in the placental vein were measured. From these data the vascular resistance of the maternal vascular bed was calculated to be only 0.8 mm Hg min/ml. A driving pressure of about 10 mm Hg maintains the probably normal placental blood flow. The vascular resistance was found to be independent of the blood pressure and the blood flow.