Variability of uterine blood flow in lactating cows during the second half of gestation

Effect of xylazine, isoxsuprine, and lidocaine on Doppler sonographic uterine and umbilical blood flow measurements in cows during the last month of pregnancy

“…An analogous increase also occurred in pregnant women and was interpreted as a sequel to the increase in blood volume, which accounts for up to 45% throughout the entire gestation period. In agreement with other studies, we did not observe an increase in fetal pulse rate, even though an increased demand on the cardiovascular system during fetal development appears obvious [8,32]. This demand is most likely met instead by the increasing size and efficiency of the heart in bovine as well as human fetuses [33,34].…”

“…The diameters of the AUT and AUM did not change significantly during the study period, which was in agreement with another study in which no diameter changes were seen in cows from week 37 to 39 of gestation [8,35]. However, the mean DM of the contralateral AUT was significantly greater in week -3 (3.2 %) and -2 (3.0 %) than in the last week of the study period.…”

“…Monthly monitoring of the uterine arteries for diameter, TAMV, BFV, and RI was also done in cows and revealed marked changes throughout gestation [6,8]. There were local adaption processes but also indications that the changes documented in the uterine arteries are changes that affect the entire cardiovascular system.…”

“…Doppler sonography has also been used to study uterine perfusion in cows during normal pregnancy [6][7][8]. Because the AUT provide the major portion of blood supply to the bovine uterus, changes in blood flow in these vessels reflect changes in uterine perfusion [9].…”

“…Time-averaged maximum blood flow velocity (TAMV) increased and resistance index (RI), which measures vascular resistance in tissues distal to the point of examination, decreased during pregnancy [6]. Another study showed a massive increase in blood flow volume during the second half of gestation as a function of the birth weight of the calf [8]. The increase was based mainly on an increase in the diameter of blood vessels rather than on an increase in blood flow velocity.…”