Background: Traditionally, a carbohydrate-rich diet in the days preceding an oral glucose tolerance test (OGTT) has been recommended based on classic studies in non-pregnant individuals showing that carbohydrate restriction elevates post-load glucose levels. Instructions on carbohydrate intake given to pregnant women having an OGTT for gestational diabetes (GDM) diagnosis vary. We tested if self-reported carbohydrate intake in pregnancy is associated with OGTT results.
Methods: Pregnant women (N=79) with ≥ 1 risk factor for GDM underwent a fasting 75 g OGTT at 24-30 wks gestation and completed a 24-hr dietary recall using a validated self-administered instrument. We tested for an association between carbohydrate intake in the 24 hrs preceding the OGTT and 1-hour OGTT glucose using linear regression, with adjustment for age, BMI, gestational age, race, and total caloric intake. We also tested for associations with 30-minute and 2-hour OGTT glucose and glucose area under the curve (AUC).
Results: Women with lower carbohydrate intake (<median=235g) were slightly older (34 vs. 32 yrs, P=0.03), but otherwise similar to women with higher intake (BMI, history of GDM in a prior pregnancy, race/ethnicity, fasting glucose). We observed a graded linear relationship between carbohydrate intake and 1-hour OGTT glucose. For every 50 g reduction in carbohydrate intake, there was a 6.2 mg/dl increase in 1-hour OGTT glucose (β=6.2 mg/dl, P<0.01); this remained significant in the adjusted model (β=7.7 mg/dl, P=0.03). Lower carbohydrate intake was also associated with higher 30-minute (unadjusted β=4.4 mg/dl, P<0.01; adjusted β=6.7 mg/dl, P=0.02) and 2-hour OGTT glucose (unadjusted β=4.3 mg/dl, P=0.03; adjusted β=6.9 mg/dl, P=0.05) and glucose AUC (unadjusted β=513, P<0.01; adjusted β=683, P=0.03). Results did not change after excluding women with intake <1000 calories or when % carbohydrate intake was used as the predictor variable.
Conclusion: Carbohydrate restriction or excess before an OGTT may affect the diagnosis of GDM.
E. Rosenberg: None. K. James: None. J. Arenas: None. M.J. Callahan: None. M. Cayford: None. S. Nelson: None. S.N. Bernstein: None. R. Thadhani: None. E.W. Seely: None. C.E. Powe: None.
National Institutes of Health (K23DK113218); Robert Wood Johnson Foundation; Harold Amos Medical Faculty Development Award (72456)