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The genetic pathogenesis of selective intrauterine growth restriction (sIUGR) remains elusive, with evidence suggesting an important role of epigenetic factors such as microRNAs. In this study, we explored the relevance of miR-373-3p to the occurrence of sIUGR. Hypoxia enhanced the levels of miR-373-3p and hypoxia-inducible factor (HIF)-1α, while HIF-1α knockdown not only boosted the migration and proliferation of HTR8 cells but also suppressed the hypoxia-induced upregulation of miR-373-3p and SLC38A1. By contrast, HIF-1α overexpression induced miR-373-3p downregulation and SLC38A1 upregulation, reducing cell growth and migration, which could be reversed by a miR-373-3p inhibitor. Importantly, the miR-373-3p inhibitor and mimic reproduced phenomena similar to those induced by HIF-1α downregulation and overexpression, respectively (including altered SLC38A1 expression, mTOR activation, cell growth, and migration). Mechanistically, the miRNA regulated cell behaviors and related mTOR signaling by targeting SLC38A1 expression through an interaction with the 3 ′ -untranslated region of SLC38A1. The placental tissues of smaller sIUGR fetuses exhibited miR-373-3p and HIF-1α upregulation, SLC38A1 downregulation, and activated mTOR. Overall, miR-373-3p appears to restrict the growth and migration of HTR8 trophoblast cells by targeting SLC38A1, as observed in the placental tissues associated with smaller sIUGR fetuses, and it could have utility in the diagnosis and treatment of this disorder. [ABSTRACT FROM AUTHOR]