Effects of food or protein restriction on plasma volume expansion in pregnant rats.

The effects of either food restriction or a low protein diet on the plasma volume expansion of pregnancy was determined in Sprague-Dawley rats. Rats fed ad libitum a standard diet or fed a 25% casein diet were used as controls. Both the food restricted and protein restricted rats had a significant reduction in body weight and fetal and placental weights. The total plasma volumes were also significantly lower in the restricted groups. Plasma volume expressed per 100 g of maternal net body weight or 100 g of conceptus weight was significantly reduced only in the rats fed the 6% casein diet. Correlations between plasma volume and maternal net body weight or conceptus weight in the control groups suggested that although the conceptus can influence the degree of expansion of maternal plasma volume, maternal factors such as net body weight are more important determinants of plasma volume expansion.