Maternal Vitamin A and Zinc Status in Relation to Placental Physiology and Fetal Growth Outcomes: A Systematic Review

Abstract

Maternal micronutrient status influences placental function and fetal development. Vitamin A and zinc contribute to cellular differentiation, immune regulation, antioxidant defense, nutrient transport, and fetal growth; however, their associations with placental and neonatal outcomes remain heterogeneous across populations and study designs. Objectives: To systematically synthesize contemporary evidence on maternal vitamin A and zinc status in relation to placental physiology, maternal–fetal micronutrient transfer, fetal growth, and neonatal outcomes, while evaluating the consistency, methodological quality, and limitations of the available evidence. Methods: This systematic review followed PRISMA 2020 guidance. Primary human studies published from January 2020 to December 2025 were identified from PubMed/MEDLINE, Scopus, and Web of Science. Reviews, meta-analyses, pilot studies, case reports, and case series were excluded. Study selection, data extraction, and risk-of-bias assessment were performed independently by two reviewers. Results: Out of 358 records identified, 19 studies were included, comprising 12 predominantly examining zinc and seven examining vitamin A. Zinc status was most frequently associated with birth weight, small-for-gestational-age status, neonatal anthropometry, and maternal–fetal zinc transfer, although some studies reported discordant or inverse associations. Vitamin A studies supported associations with placental retinol transfer and fetal-growth regulation, including nonlinear relationships. Conclusions: Maternal vitamin A and zinc status are associated with placental nutrient handling and fetal growth, but the available evidence is heterogeneous and predominantly observational. Zinc showed comparatively consistent relationships with birth weight and SGA, whereas vitamin A was more closely related to retinol transfer and fetal growth regulation.