We studied the relationship between 1-h glucose response and the percentage of carbohydrates in a given meal in 14 gestational diabetic women who did not require insulin therapy and were between 32 and 36 wk gestation. Each subject was > 130% ideal body weight and was placed on a diet of 24 kcal · kg−1 · 24 h−1, with 12.5% of calories at breakfast and 28% of the calories at lunch and again at dinner, with other calorie intake divided among three snacks. Glycemic response was monitored by self-monitoring of blood glucose 1 h after the start of each meal. Ten postprandial values for each meal were averaged for each of the 14 women. The correlation between percentage of carbohydrates and postprandial glucose level at 1 h was strongest for dinner (r = 0.95, P < 0.001), with more variability seen at breakfast (r = 0.75, P = 0.002) and lunch (r = 0.86, P = 0.001). To maintain a 1-h postprandial whole-blood glucose level <7.78 mM required the following percentages of carbohydrates in each meal: 45% at breakfast, 55% at lunch, and 50% at dinner. If 1-h postprandial whole-blood glucose level was to remain <6.67 mM, then the respective values were 33, 45, and 40%. We conclude that the glycemic response to a mixed meal in subjects with gestational diabetes is highly correlated with the percentage of carbohydrates of the ingested meal and varies among individuals and among breakfast, lunch, and dinner. These results emphasize the potential hazard of rote prescription of diets relatively high in carbohydrates during pregnancy complicated by gestational diabetes and the need to validate diet prescriptions with blood glucose monitoring.

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