Carbohydrate Intake and Oral Glucose Tolerance Test Results in the Postpartum Period.

CONTEXT: The American Diabetes Association (ADA) recommends a 3-day preparatory diet prior to a diagnostic oral glucose tolerance test (OGTT), a test often recommended in postpartum individuals with a history of gestational diabetes (GDM). OBJECTIVE: Evaluate the relationship between carbohydrate intake and OGTT glucose in 2 cohorts of postpartum individuals. METHODS: We performed analyses of postpartum individuals from 2 prospective studies with recent GDM (Balance after Baby Intervention, BABI, n = 177) or risk factors for GDM (Study of Pregnancy Regulation of INsulin and Glucose, SPRING, n = 104) .We measured carbohydrate intake using 24-hour dietary recalls (SPRING) or Food Frequency Questionnaire (BABI) and performed 2-hour 75-g OGTTs. The main outcome measure was 120-minute post-OGTT glucose. RESULTS: There was no relationship between carbohydrate intake and 120-minute post-OGTT glucose level in either study population (SPRING: ß = 0.03, [-5.5, 5.5] mg/dL, P = .99; BABI: ß = -3.1, [-9.5, 3.4] mg/dL, P = .35). Adding breastfeeding status to the model did not change results (SPRING ß = -0.14, [-5.7, 5.5] mg/dL, P = .95; BABI ß = -3.9, [-10.4, 2.7] mg/dL, P = .25). There was, however, an inverse relationship between glycemic index and 120-minute post OGTT glucose (BABI: ß = -1.1, [-2.2, -0.03] mg/dL, P = .04). CONCLUSION: Carbohydrate intake is not associated with post-OGTT glucose levels among postpartum individuals. Dietary preparation prior to the OGTT may not be necessary in this population.

Relationship between carbohydrate intake and oral glucose tolerance test results among pregnant women.

AIMS: Evaluate the relationship between self-reported carbohydrate intake and oral glucose tolerance test (OGTT) results in pregnancy. METHODS: We measured carbohydrate intake using 24-hour dietary recall and performed a 2-hour 75-gram OGTT in 95 pregnant women with risk factors for gestational diabetes (GDM) at a median of 26 weeks' gestation. We tested for associations between carbohydrate intake in the 24 hours preceding the OGTT and 60-minute OGTT glucose, glucose at other timepoints, and glucose area under the curve (AUC) using linear regression, with adjustment for potential confounders. RESULTS: We observed an inverse linear relationship between carbohydrate intake (median 237 grams [interquartile range: 196, 303]) and 60-minute OGTT glucose. For every 50 gram reduction in carbohydrate intake, there was an 8.9 mg/dl increase in 60-minute OGTT glucose (P < 0.01) in an adjusted model. Lower carbohydrate intake was also associated with higher 30-minute (adjusted ß = -6.5 mg/dl, P < 0.01) and 120-minute OGTT glucose (adjusted ß = -8.1 mg/dl, P = 0.01) and AUC (adjusted ß = -767, P < 0.01). CONCLUSIONS: Carbohydrate intake in the day preceding an OGTT in pregnancy is associated with post-load glucose values, with lower carbohydrate intake predicting higher glucose levels and higher carbohydrate intake predicting lower glucose levels. Carbohydrate restriction or excess before an OGTT may affect GDM diagnosis.