Effect of low carbohydrate diets during pregnancy on parturition and postnatal survival of the newborn rat pup.

To test the hypothesis that maternal dietary carbohydrate is essential for the postnatal survival of the newborn rat pup, two experiments were designed. Pregnant dams were fed one of two basal carbohydrate-free diets. In experiment 1, the primary energy source was edible oleic acid; in experiment 2, it was soybean oil. Supplemental glucose was substituted for lipid. In experiment 1, pregnant dams were fed 4% dietary glucose for d 0-8 to allow successful implantation, as shown previously. Beginning on d 9 the dams were fed 0, 2, 4, 8, 12 or 62% glucose. Control dams (62% glucose) normally delivered pups weighing 5.6 g on d 21. Dams fed zero glucose delivered pups, weighing 3.1 g, 2 d late. The survivability of the litters increased with maternal dietary carbohydrate. All pups from dams fed 0-4% glucose died within 48 h. Pup survival to d 7 was 10% at 8% glucose, 23% at 12% glucose and 82% at 62% glucose. In experiment 2 soybean oil-based diets (basal supplied ca. 4% glycerol) with 0, 4, 12 and 62% glucose were fed from d 0. At zero glucose, fewer dams delivered late and birth weights were greater than in experiment 1. However, all pups born to zero-glucose dams died by d 4. Pup survival to d 7 was 48% at 4% glucose and 84% at 12% glucose. The data demonstrate that maternal dietary carbohydrate is required for fetal growth, normal parturition and postnatal survival of rat pups. The results indicate that late gestation, parturition and the neonatal period may be especially vulnerable to maternal carbohydrate deprivation.