Effects of vitamin and multiple micronutrient supplementation for pregnant and/or lactating women on maternal and infant nutritional status in low- and middle-income countries: a systematic review and meta-analysis

Globally, over half of women of reproductive age are affected by at least one micronutrient deficiency, often exacerbated during pregnancy and lactation, contributing to adverse maternal and child health outcomes. This systematic review and meta-analysis synthesized impact of vitamin supplementation on maternal, infant and lactational nutritional status in low- and middle-income countries. MEDLINE, EMBASE, CENTRAL, and WHO library databases were searched. Eligible studies included randomized controlled trials of micronutrient supplementation in healthy pregnant/lactating women, assessing maternal/infant micronutrient status or milk composition. Random-effects meta-analysis was performed for outcomes with ≥2 studies, and evidence quality was evaluated using GRADE. Eighty-seven papers (76 trials, including 65 for meta-analysis) were included. Maternal vitamin B-12 supplementation during pregnancy increased serum cobalamin levels (standard mean difference SMD 0.39; 95% CI 0.11, 0.68; P=0.01) and reduced deficiency (OR 0.43; 95% CI 0.19, 0.95; P=0.04), with improved B-12 concentrations in milk, especially when administered postpartum (SMD 0.33; 95% CI 0.02, 0.63; P=0.04), but had no consistent effect on infant or cord serum cobalamin levels. Vitamin A supplementation during pregnancy or postpartum improved maternal serum levels (SMD 0.57; 95% CI 0.12, 1.01; P=0.01) and reduced deficiency at thresholds ≤0.7 μmol/L (OR 0.57; 95% CI 0.45, 0.73; P<0.001); however, its effects on infant and cord serum levels were negligible. Postpartum vitamin A supplementation improved milk vitamin A concentrations (SMD 0.53; 95% CI 0.19, 0.86; P<0.001), particularly with single high-dose regimens. Supplementation with vitamin D during pregnancy increased maternal serum vitamin D levels (SMD 0.89; 95% CI 0.55, 1.24; P<0.001), reduced deficiency at thresholds ≤50 nmol/L (OR 0.30; 95% CI 0.14, 0.64; P<0.001) and increased vitamin D levels in infant and cord serum. Micronutrient supplementation during pregnancy and lactation improved maternal nutritional status but showed inconsistent effects on infant nutritional status, highlighting the need for further research. CRD42022308715; https://tinyurl.com/y33cxekr.