Background: Obstetric outcomes in women consuming low carbohydrate diets have reported conflicting results. The majority of these studies have defined low carbohydrate intake by the proportion that carbohydrates contribute to overall caloric intake. We hypothesised that a low absolute carbohydrate intake affects obstetric outcomes differently than a low relative carbohydrate intake.
Methods: Detailed dietary data was collected in women enrolled in the Study of Probiotic IN Gestational diabetes (SPRING) at both 16 and 28 weeks’ gestation by food frequency questionnaire. Obstetric outcomes were compared between women consuming a low carbohydrate diet (LCD) defined as carbohydrate content of less than 100 grams per day and women consuming a standard diet (SD) defined as greater than 100 grams of carbohydrate per day independent of overall energy intake.
Results: Mean gestation was increased in women consuming a LCD at 16 and/or 28 weeks’ gestation, compared with women consuming a SD. The difference was greatest when women consumed a LCD at both 16 and 28 weeks’ gestation (16: 39.7 vs 39.2 weeks, p = 0.02; 28: 39.9 vs 39.2 weeks, p = 0.02; 16 and 28: 40.1 vs 39.2, p = 0.0025). Gestation was not increased in women consuming a diet where carbohydrate contributed to less than 40% of overall energy intake. Birth centile was decreased in offspring of women consuming a LCD at 28 weeks’ gestation, but not in women consuming a LCD at 16 or both 16 and 28 weeks’ gestation. No other statistically significant differences in obstetric outcomes were observed.
Conclusion: Consumption of less than 100 grams of carbohydrate per day in pregnancy is associated with increased gestational age at delivery.