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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 gestational diabetes (GDM) risk factors 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 range196, 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- (adjusted β=-6.5 mg/dl, P<0.01) and 120-minute OGTT glucose (adjusted β=-8.1 mg/dl, P=0.01) and AUC (adjusted β=-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.