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 pr edispose 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 nes ted factorial model with and without food intake as a covariate was em ployed. Both greater exercise intensity and the lower levels of dietar y carbohydrate independently decreased term maternal liver and plantar is 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, ind icating that energy deficits modulated these exercise effects. In cont rast, for the offspring, when food intake was controlled for, a restri cted level of maternal dietary carbohydrate significantly lowered feta l weight, plasma glucose and insulin concentrations and liver glycogen concentrations measured at term. Exercise alone did not reduce mean f etal weight if nested weights within a litter were used in the statist ical analysis. Mild to moderate maternal exercise lowered only fetal p lasma glucose concentrations and only if maternal food intake was not controlled for. These results indicate that acute exercise during preg nancy can have detrimental effects on fetal development only if dietar y glucose is severely restricted. Otherwise, adequate glucose and ener gy in the maternal diet in untrained pregnant rats during repeated bou ts of acute exercise seem to protect the fetus.