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.