Interaction of maternal blood volume and uterine blood flow with porcine fetal development.

Abstract

The relationships of maternal nutrition, blood volume and uterine blood flow to porcine fetal development were investigated in domesticated pigs that normally experience 40% fetal loss. Yorkshire pigs were subjected to prolonged inanition (40 days; 0 kcal/day; water only) from Days 50 to 90 of pregnancy and either hysterectomized on Day 90 or realimented to a full diet and allowed to advance to parturition; controls received a full diet (7028 kcal/day) until hysterectomy at Day 90 or throughout gestation. Although a marked decline in body weight (−31 kg) occurred in gilts subjected to inanition, fetal survival rates, litter weight, as well as the number of live Day 90 fetuses or number of live piglets born were similar in starved and full-fed animals. Blood hemoglobin, packed cell volume, plasma protein, erythrocyte and leukocyte populations during inanition were maintained at levels similar to those of controls with the exception of shifts in concentration caused by plasma volume changes. Plasma volume (r=0.65) and blood volume (r=0.58) were highly correlated with body weight in inanition and control dams throughout the period of inanition and realimentation. Uterine blood flow during late pregnancy was similar in all experimental and control dams, and remained constant with time in spite of a 13-fold increase in fetal weight and regardless of marked fluctuations in plasma and blood volumes. Uterine blood flow was highly correlated with Day 90 litter size (r=0.82) and fetal weight (r=0.86). Severe nutrient deprivation during late pregnancy in the pig results in a marked decline in maternal body weight, plasma volume and blood volume; however, maternal uterine blood flow is maintained at a level similar to full-fed controls. Maintenance of uterine blood flow suggests that selective distribution of cardiac output, coincident with adequate blood constituent levels, may allow normal porcine fetal development during prolonged starvation.