Impact of maternal micronutrient supplementation on pregnancy outcomes in developing countries: a systematic review and meta-analysis

Background Poor pregnancy outcomes are still relatively high in developing countries. Deficiency in micronutrients is among the factors that play a role in developing adverse pregnancy outcomes. The present study aims to investigate the role of micronutrient deficiencies in poor pregnancy outcomes and their association with newborn health. Method For this review, a systematic search was done using the Harzing Perish and publish software, as well as separate searches in PubMed, Google Scholar, Web of Science, and Scopus for evidence on the association between maternal micronutrient status and/or micronutrient supplementation during pregnancy and adverse pregnancy outcomes, including low birth weight (LBW) and small for gestational age (SGA). We assessed heterogeneity using the I2 index, conducted the meta-analysis, and measured the overall effect size using the fixed-effect method. Results Overall, 49 articles were included in this systematic review, and 43 articles were included in the meta-analysis. Cumulative analysis of effect size showed that supplementation of vitamin D (d = 0.18), zinc (d = 0.39), iron with folic acid (d = 0.64) or multiple micronutrients (d = 0.059) plays positive role in reducing the risk of LBW and SGA. However, in all studies apart from iron with folic acid the effect of Multiple Micronutrient Supplementations (MMS) or other single micronutrient was assessed against the control group receiving iron with folic acid. Conclusion Iron with folic acid showed the strongest and most consistent effect in reducing LBW and SGA; however, zinc, vitamin D, and multiple micronutrient supplementation were also associated with modest improvements in fetal growth outcomes. The topic and protocol were retrospectively registered in PROSPERO (ID: CRD42023451468).