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.

Introduction: Effective perioperative management in cesarean section remains essential to optimize maternal outcomes. Melatonin (M) has been proposed as a potential adjunct due to its analgesic, anxiolytic, and antiemetic properties; however, evidence from randomized controlled trials (RCTs) remains inconsistent. This meta-analysis aimed to evaluate the efficacy and safety of preoperative melatonin compared with placebo in women undergoing cesarean section. Methods: A systematic search was conducted in PubMed, Scopus, and Cochrane from inception to 15 March 2026 for studies evaluating pregnant women undergoing elective cesarean section receiving preoperative melatonin versus placebo (P) (PROSPERO “CRD420261355468”). Heterogeneity was assessed using the I² statistic and Cochrane Q test. Risk ratios (RRs) and standardized mean differences (SMDs) were computed using a restricted maximum-likelihood estimator random-effects method. Trial Sequential Analysis (TSA) was performed to assess the robustness and sufficiency of the evidence. Results: Seven RCTs were included with 552 patients (melatonin: 278; placebo: 274). Preoperative melatonin significantly reduced opioid consumption in the overall pooled analysis (RR 0.31, 95% CI 0.12 to 0.80; p = 0.030; I² = 50%), and TSA supported the robustness of this opioid-sparing finding under the selected assumptions. Postoperative pain scores were also significantly lower in the melatonin group (SMD −2.10, 95% CI −2.43 to −1.78; p < 0.01; I² = 22%). The incidence of postoperative nausea showed a trend toward reduction in the conventional meta-analysis (RR 0.49, 95% CI 0.23–1.04; p = 0.057; I² = 34%); although TSA suggested a possible benefit, this finding should be considered exploratory. No significant difference was observed in intraoperative blood loss (SMD −0.33, 95% CI −1.53 to 0.88; p = 0.60; I² = 94%). Conclusions: Preoperative melatonin may be a promising adjunct in cesarean section, particularly for reducing postoperative pain and overall opioid consumption. TSA findings support the opioid-sparing result under selected assumptions, while the possible effect on postoperative nausea remains exploratory. Further high-quality trials are warranted before routine clinical implementation can be recommended.