Effects of Nutritional Interventions During Pregnancy on Maternal and Neonatal Outcomes: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

Background: Maternal undernutrition is associated with impaired fetal growth and adverse pregnancy outcomes, but the effects of food-based nutritional interventions during pregnancy remain uncertain. This systematic review and meta-analysis evaluated their effects on maternal and neonatal outcomes using evidence exclusively from randomized controlled trials (RCTs). Methods: PubMed, Embase, Scopus, and the Cochrane Library were searched from inception to 15 July 2026 for RCTs comparing food-based nutritional interventions with standard care, no supplementation, micronutrient supplementation, or an alternative nutritional intervention. Risk ratios (RRs) for binary outcomes were pooled using the Mantel-Haenszel method, while mean differences (MDs) for continuous outcomes were pooled using the inverse-variance method. Restricted maximum-likelihood random-effects models were applied, and heterogeneity was assessed using I2 and Cochran's Q test. The protocol was registered in PROSPERO (CRD420261465279). Results: Six RCTs comprising 6245 participants were included, of whom 3150 (50%) received a nutritional intervention. Nutritional interventions increased birth weight (MD 51.49 g; 95% CI 22.87-80.11; I2 = 42.7%; p < 0.01) and birth length (MD 0.29 cm; 95% CI 0.14-0.45; I2 = 21.6%; p < 0.01). No significant effects were observed on birth head circumference (MD -0.14 cm; 95% CI -0.62 to 0.34; I2 = 73.9%; p = 0.57), low birth weight (RR 0.76; 95% CI 0.35-1.68; I2 = 64.2%; p = 0.28), stillbirth (RR 0.96; 95% CI 0.78-1.19; I2 = 0%; p = 0.61), or miscarriage (RR 0.83; 95% CI 0.35-1.97; I2 = 0%; p = 0.45). Conclusions: Food-based nutritional intervention strategies were associated with small statistically significant increases in birth weight and birth length; however, the clinical importance of differences of approximately 51 g and 0.29 cm remains uncertain. Evidence was inconclusive for low birth weight, head circumference, stillbirth, and miscarriage.