Impact of carbohydrate quantity and quality on maternal and pregnancy outcomes in gestational diabetes mellitus: A systematic review and meta-analysis

Objective: To evaluate the impact of carbohydrate quantity and quality on maternal and pregnancy outcomes in gestational diabetes mellitus. Methods: Using a pre-defined search strategy, two researchers systematically searched MEDLINE, CINAHL Plus, and PubMed for randomized controlled trials comparing low-carbohydrate, low-glycaemic index, or lowglycaemic load diets with usual care in gestational diabetes mellitus. Mean differences and risk ratios were extracted. Results: Thirteen studies with 877 participants were included. Low-carbohydrate diet did not significantly differ from usual care for fasting blood glucose (3 studies; mean difference: 1.60 mmol/L; 95 % confidence interval: -1.95, 5.15), insulin requirement (2 studies; risk ratio: 1.01; 95 % confidence interval: 0.31, 3.05), birthweight (4 studies; mean difference: -0.23 kg; 95 % confidence interval: -1.90, 1.45), caesarean delivery (5 studies; risk ratio: 1.11; 95 % confidence interval: 0.66, 1.85), macrosomia (3 studies; risk ratio: 0.35; 95 % confidence interval: 0.00, 2130.64), large-for-gestational-age (2 studies; risk ratio: 0.46; 95 % confidence interval: 0.03, 7.20), and small-for-gestational-age infants (2 studies; risk ratio: 0.94; 95 % confidence interval: 0.00, 231.18). Lowglycaemic index diet did not significantly differ from usual care for the above outcomes either. However, lowglycaemic load diet reduced macrosomia risk (2 studies; risk ratio: 0.51; 95 % confidence interval: 0.43, 0.59). Conclusions: Low-carbohydrate and low-glycaemic index diets do not differ from usual care for most maternal and foetal outcomes in gestational diabetes mellitus. But low-glycaemic load diet may reduce macrosomia risk.