Gestational diabetes mellitus (GDM) increases fetal morbidity/mortality, and is associated with elevated risks of offspring cardiometabolic disease. These risks are compounded in infants born large for gestational age (LGA) rather than appropriate size (AGA), a common complication of GDM associated with altered placental function. Circulating extracellular vesicle (EV)-associated miRNAs are internalised into the placenta and are emerging as key GDM mediators, with their role in LGA yet to be explored. We hypothesise that maternal EV-miRNAs may alter placental function in concurrent GDM-LGA. Serum was collected from GDM women (2628 weeks). Birth outcomes and placental tissue were collected at delivery. EV-associated miRNAs were profiled using qPCR arrays (n=7) which showed that miR-200c-3p (2.78-fold; P<0.05 vs. AGA) and miR-375 (4.74-fold; P<0.01 vs. AGA) were elevated in the sera of GDM women with LGA infants and in the placentas of a separate cohort (P<0.05 vs. AGA; qPCR). Gene ontology enrichment analysis identified that predicted targets (e.g. insulin-like growth factor receptor-1 (IGF1R), a key regulator of placental proliferation) of these miRNAs are central to placental metabolism/development. To functionally confirm these predictions, miR-200c-3p and miR-375 were overexpressed in the placental BeWo cell-line (miR-200c-3p 8000-fold, P<0.05; miR-375 13-fold, P<0.05; n=4) or normal human term placental explants (miR-200c-3p 9-fold, P<0.05; miR-375 30-fold, P<0.05; n=3) by transfecting with specific miRNA-mimics or non-targeting control (NT; 100 nM; 73 h). The percentage of proliferative Ki67+ve BeWo cells (fluorescence immunocytochemistry) was reduced by miR-200c (−17%; P<0.01 vs. NT) and miR-375 (−19%; P<0.05 vs. NT) transfection (n=10). Preliminary Western blot data indicates a trend towards decreased IGF1R in placental explants overexpressing miR-375 (56% reduction vs. NT; n=3). These data demonstrate that miR-200c-3p and miR-375 miRNAs elevated with concurrent GDM and LGA in maternal serum/placenta with concurrent GDM-LGA alter placental proliferation, potentially linking maternal serum components to fetal growth in GDM.