The Effect of Maternal Water Deprivation on Ovine Fetal Blood Volume

Abstract

SUMMARYFetal blood volume was measured in pregnant ewes bearing chronically cannulated fetuses in the last third of gestation. The increase in fetal blood volume secondary to growth was established from serial measurements in four control animals. The effect ofmaternal dehydration was assessed by measuring the change in fetal blood volume during twelve episodes of maternal water deprivation in another six ewes. Fetal blood volume increased during each episode of maternal dehydration. In five experiments the rate of increase was greater than controls and in seven experiments the rate of increase was less than controls. Thus, fetal hypovolaemia does not occur during maternal dehydration in the ovine fetus in the last third of gestation.

Role of fetal sac fluids during maternal water deprivation in sheep

“…It was therefore preferable to studying two groups of animals at the same gestational age, given previous findings that the responsiveness of the fetus to maternal water deprivation (as measured by plasma osmolality, by urine osmolality and production and by plasma concentration of arginine vasopressin (AVP)) is similar over the age range of 124-144 days (Bell, Congiu, Hardy & Wintour, 1984;Ross et al 1988;Schreyer, Sherman, Ervin, Day & Ross, 1990). Furthermore, exposing fetuses to more than one period of maternal water deprivation does not significantly alter their responses to this experimental procedure (Bell et al 1984;Bell & Wintour, 1985). Consequently, gestational age and prior exposure to maternal water deprivation should have minimal effects on our results.…”

“…This indicates that gestational effects on the responsiveness of the ewe and the fetus to maternal water deprivation were minimal. Previous studies (Bell et al 1984;Bell & Wintour, 1985) indicate that prior exposure to water deprivation does not appear to change the responsiveness of the ewe or her fetus to this experimental procedure. Consequently, any differences that we found in the response to maternal water deprivation at 135 days compared with 127 days are likely to be due to an absence of fluid in the fetal sacs, and not to the different fetal ages or the prior exposure.…”

Alterations in Maternal Corticosteroid Levels Influence Fetal Urine and Lung Liquid Production

“…Evidence suggests that altering the osmotic gradient across the placenta can influence water delivery across the placenta. 1 (1,24 There was a significant overall decrease in fetal osmolality in the low aldosterone groups, which could decrease the mother-to-fetus transfer rate; however, the maternal-fetal osmotic gradient was not changed significantly.…”