Fetal rabbit intestinal absorption: implications for transamniotic fetal feeding.

Delivery of nutrients to the fetus via the developing gastrointestinal tract has been advocated as a potential prenatal treatment for intrauterine growth retardation. Previous studies have demonstrated significant increases in fetal length and weight following continuous intraamniotic nutrient infusions in animals. The ideal composition of intraamniotic feedings has yet to be determined. Thirteen time-mated rabbit does underwent ceserean section between gestational days 27 and 33 to deliver 54 fetuses. The everted intestinal sleeve technique was used to measure radiolabeled carbohydrate and amino acid uptake rates from 1-cm segments of midjejunum. Uptake of galactose was more than double that of glucose and fructose. Active uptake of glucose, fructose, and galactose increased by 3.3-fold, 6.2-fold, and 2.1-fold, respectively, during the final 7 days of gestation when expressed as uptake per mg intestine. In contrast, uptake of the amino acids leucine, lysine, and proline decreased by 41%, 34%, and 17%, respectively, during the final 5 days of gestation. The demonstrated changes in intestinal absorption and nutrient delivery in the rabbit model, during the last days of gestation, suggest that certain substrates are absorbed more rapidly than others. Galactose may be the preferred intraamniotic carbohydrate for fetal growth.