Consumption of a Low Carbohydrate Diet in Overweight or Obese Pregnant Women Is Associated with Longer Gestation of Pregnancy

Studies of obstetric outcomes in women consuming low-carbohydrate diets have reported conflicting results. Most studies have defined low-carbohydrate diets by the percentage that carbohydrates contribute to overall energy intake, rather than by an absolute amount in grams per day (g/d). We hypothesised that a low absolute carbohydrate diet affects obstetric outcomes differently than a low percentage carbohydrate diet. Dietary data were collected from overweight or obese women in the Study of Probiotic IN Gestational diabetes at 16- and 28-weeks’ gestation. Obstetric outcomes were compared between women whose carbohydrate intake was in the lowest quintile vs quintiles 2–5. Mean gestation was increased in women whose absolute carbohydrate intake was in the lowest quintile at 16 and at both 16- and 28-weeks’ gestation compared with all other women (16: 39.7 vs. 39.1 weeks, p = 0.008; 16 and 28: 39.8 vs. 39.1, p = 0.005). In linear regression analysis, a low absolute carbohydrate intake at 16 and at 28 weeks’ gestation was associated with increased gestation at delivery (16: p = 0.04, adjusted R2 = 0.15, 28: p = 0.04, adjusted R2 = 0.17). The coefficient of beta at 16 weeks’ gestation was 0.50 (95% CI 0.03–0.98) and at 28 weeks’ gestation was 0.51 (95%CI 0.03–0.99) meaning that consumption of a low absolute carbohydrate diet accounted for an extra 3.5 days in gestational age. This finding was not seen in women whose percentage carbohydrate intake was in the lowest quintile. Low-carbohydrate consumption in pregnancy is associated with increased gestational age at delivery.