Maternal dietary carbohydrate restriction and mild-to-moderate exercise during pregnancy modify aspects of fetal development in rats.

To determine whether acute bouts of exercise during pregnancy would predispose the fetus to increased risk if maternal dietary carbohydrate were restricted, untrained pregnant rats were randomly assigned to a 0% (low), 12% (moderate) or 60% (high) glucose diet, and either rested or exercised daily for 20 min from d 16 to term on a rodent treadmill at a mild (15.5 m/min) or moderate (24.3 m/min) intensity. A 3 x 3 nested factorial model with and without food intake as a covariate was employed. Both greater exercise intensity and the lower levels of dietary carbohydrate independently decreased term maternal liver and plantaris glycogen concentrations and increased plasma lactate concentrations. However, significant differences due to exercise disappeared (except for plasma lactate) with food intake controlled for in the model, indicating that energy deficits modulated these exercise effects. In contrast, for the offspring, when food intake was controlled for, a restricted level of maternal dietary carbohydrate significantly lowered fetal weight, plasma glucose and insulin concentrations and liver glycogen concentrations measured at term. Exercise alone did not reduce mean fetal weight if nested weights within a litter were used in the statistical analysis. Mild to moderate maternal exercise lowered only fetal plasma glucose concentrations and only if maternal food intake was not controlled for. These results indicate that acute exercise during pregnancy can have detrimental effects on fetal development only if dietary glucose is severely restricted. Otherwise, adequate glucose and energy in the maternal diet in untrained pregnant rats during repeated bouts of acute exercise seem to protect the fetus.