In GDM placentae, the number of pan-macrophage (CD68), HBC-enriched (FOLR2), and M2-associated (CD163, MRC1) cells were reduced in terminal villi compared with non-GDM controls (p < 0.05; n = 13 non-GDM; n = 12 GDM), indicating reduced HBC abundance without phenotypic switching. This evidence concerns the gene MRC1 and gestational diabetes.