Uteroplacental Vascular Perfusion and Blood Flow during Pregnancy in the Guinea Pig

Abstract

The relationships between regional uterine blood flow (UBF), placental blood volume (maternal compartment) and fetal-placental weights and size were determined at specific gestational stages in the guinea pig. Regional variations in UBF were noted between days 27 and 65 of pregnancy (day 0 = ovulation), with the tubal third of the uterus receiving a greater flow rate than the cervical region. The middle portion of the uterus consistently received a lower UBF than did the tubal or cervical zones. Between days 35 and 50 of gestation, UBF rates were consistently lower in the middle portion of the uterus as compared to the tubal and cervical regions in animals possessing exactly three pregnancy sites in a cornu. In contrast, placental blood volume in the maternal compartment from each of the three uterine zones was quantitatively similar, even though lower placental and fetal weights were found in the middle pregnancy sites as compared to either the tubal or cervical zones. When vascular perfusion rates were calculated by determining arterial-venous flow rate differences, both the tubal and cervical uterine zones were found to be preferentially perfused as compared to the middle uterine zone. These studies demonstrate that the correlation between regional UBF rates and fetal-placental development in the guinea pig is primarily due to the greater perfusion rate through the tubal and cervical zones of the pregnant guinea pig uterus, and not due to an expanded vascular volume of the placentae in these zones.

Effects of Exercise on Fetal-Placental Growth and Uteroplacental Blood Flow in the Rat

“…Previous studies have indicated that acute reductions in U-PBF have the greatest growth-suppressant effects on the placenta [2,4], with minimal effects noted on fetal growth. The present results suggest that the exercise regime may have shunted blood flow to other body (e.g., skele tal muscle) regions which resulted in a de pressed UBF rate in exercised rats and, thus, lowered placental growth [7], The inability of the growth-retarded placenta to support the fetal demands may account for the decreased fetal viability rate in these animals relative to controls. These findings are in close agree ment with previous studies in which the pups of exercised female rats had a greater fetal mortality rate than the offspring of controls [13].…”

“…several species [2,[5][6]. Mild (acute) uterine ischemia has been demonstrated to induce fetal growth retardation, while the prolonged depression of UBF can induce fetal death [2,[5][6][7]. In addition, regional variations in UBF and vascular pressure have also been corre lated with normal variations in fetal-placen tal growth [2,4,[8][9][10], Thus, the factors which regulate uterine vascular dynamics in directly modulate the intrauterine environ ment of the developing conceptus [3,11] and All values are represented as group means (± SEM) for (n) pregnant female rats.…”

“…In addition, regional variations in UBF and vascular pressure have also been corre lated with normal variations in fetal-placen tal growth [2,4,[8][9][10], Thus, the factors which regulate uterine vascular dynamics in directly modulate the intrauterine environ ment of the developing conceptus [3,11] and All values are represented as group means (± SEM) for (n) pregnant female rats. Birth weights arc repre sented as the mean ( ± SEM) for all pups born in the respective group, a vs. b or b vs. c: p < 0.05; a vs. c: p < 0.01. may have either a supportive or detrimental effect on intrauterine growth and develop ment of the fetal-placental unit during preg nancy [2,3,7).…”

Estrogen-Regulated Uterine Vascularization Modulates the Guinea Pig Intrauterine Environment

“…At 24 h following the last E injection, a group of animals was anesthetized (methoxyflurane; PittmanMoore), laparotomized via a midventral incision and small vascular occlusion clamps were placed on each uterine artery at the uterocervical and tubal junctions for evaluation of the effects of acute arterial reduction on intrauterine parameters as previously described [17], In a corresponding group, all visible segmental arteries to the uterus arising from the uterine arteries were restricted by direct contact with a needle (22-gauge) point vascular cauterization iron. Sham-oper BiolNeonaic 1997;72:314-321ated animals (i.e.…”

“…Growth and expansion of the intrinsic uterine vascular bed has been well documented to occur in association with early blastocyst-endometrial interaction [6][7][8][9][10][11][12] and decidua growth induction [ 10,[13][14][15] and has been implicated as a mandatory requirement for the successful growth and function of the placenta [16][17][18], Acute reductions in uterine blood flow during early pregnancy have been recognized to have deleterious effects on sub sequent fetal-placental development [ 19], The chronic reduction of uterine blood flow by vascular clamping may induce fetal-placental death or resorption, whereas acute reductions in uterine hyperemia during pregnancy pro mote growth retardation of maternal and fetal tissues [20][21][22], These studies demonstrate the essential role of the uterine vascular sup ply in the establishment and maintenance of proper intrauterine environmental conditions necessary for the continued growth and devel opment of the fetal-placental unit. However, the temporal and quantitative relationships between changes in uterine vascular capacity and the associated alterations in the intrauter ine environment supporting fetal-placental development remain to be elucidated.…”