Effects of Different Nutritional Strategies on the Prevention and Management of Gestational Diabetes Mellitus: A Systematic Review and Network Meta-Analysis

Background: While nutritional interventions are pivotal for the prevention and management of gestational diabetes mellitus (GDM), the optimal nutritional strategy remains unclear. Methods: PubMed, EMBASE, Cochrane Library and Web of Science were searched for randomized controlled trials (RCTs). Eligible studies targeted both GDM-diagnosed patients and high-risk cohorts, comparing nutritional interventions with standard controls. Data were extracted and synthesized through network meta-analyses to estimate the standardized mean difference (SMD) or relative risk (RR). The primary outcomes were incidence of GDM, fasting blood glucose (FBG), HOMA-IR, glycated hemoglobin (HbA1c), gestational weight gain (GWG), and cesarean section rate (CSR). Results: A total of 59 trials involving 10,262 women evaluated 24 nutritional strategies. Among high-risk pregnant women, inositol was associated with a reduced incidence of GDM (RR = 0.50, 95% CI: 0.37, 0.68; SUCRA = 84.5%) and lower FBG levels (SMD = −0.42, 95% CI: −0.66, −0.18; SUCRA = 89.8%). For CSR in high-risk pregnant women, blueberry combined with dietary fiber showed a favorable ranking (RR = 0.30, 95% CI: 0.10, 0.90; SUCRA = 97.8%). Among patients with GDM, the Dietary Approaches to Stop Hypertension (DASH) diet showed a significant effect on HOMA-IR (SMD = −2.79, 95% CI: −4.49, −1.09; SUCRA = 95.9%). Plant sterols showed a favorable effect on HbA1c levels (SMD = −1.40, 95% CI: −2.00, −0.80; SUCRA = 95.7%). Fish oil was associated with reduced GWG (SMD = −0.44, 95% CI: −0.76, −0.12; SUCRA = 94.1%). Combined supplementation with magnesium, zinc, calcium, and vitamin D ranked favorably for CSR compared with the control group (RR = 0.44, 95% CI: 0.15, 1.29; SUCRA = 82.1%), but this finding was based on limited evidence. Conclusions: Current evidence suggests that inositol, the DASH diet, plant sterols, and fish oil may play a positive role in the prevention and management of gestational diabetes. However, the effects of interventions with very high SUCRA scores but limited supporting evidence—such as blueberries combined with dietary fiber and magnesium–zinc–calcium–vitamin D supplements—should be interpreted with caution. Well-designed, large-scale randomized controlled trials are needed in the future to further confirm these findings.