Since decreased transfer of nutrients into the fetus has been documented in many forms of intrauterine growth retardation, we evaluated whether increasing fetal nutrient availability would prevent the development of experimental growth retardation in fetal lambs. Fetuses were separated into three groups: E, animals growth retarded by repetitive uteroplacental embolization (n = 8); ES, animals treated as in E and given fetal femoral venous infusions of 5% glucose and 6.8% amino acids (n = 7); and C, controls (n = 8). The duration and density of embolization were the same in E and ES; initial physical and metabolic characteristics and gestation at delivery were similar in all groups. E birth weight was reduced 26% compared to C (2888 +/- 373 SEM g versus 3880 +/- 277 g, p less than 0.05); fetal/maternal weight ratio was decreased 35% (p less than 0.005) and ponderal index decreased 22% (p less than 0.005). Asymmetric growth retardation was indicated in E by an increased brain/body weight ratio (p less than 0.05). ES fetuses, in contrast, showed no differences from C in birth weight (3601 +/- 190 g) or body proportions. ES were larger than E, with a greater fetal/maternal weight ratio and ponderal index (p less than 0.05 for both). In E and ES, size at birth showed a positive relation to the amount of supplements received. The average daily supplementation rate correlated with the fetal/maternal weight ratio and with the ponderal index (for both r = 0.62, p less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)