The precise physiological role of uteroglobin is not yet known. Putative functions are:
# Immunomodulation
# Progesterone binding: weak in some animals, especially weak in humans. (Note: UGB is itself progesterone induced gene in the endometrium in Lagomorphs)
# Inhibits phospholipase A2 in vitro
# Binds phosphatidylcholine, phosphatidylinositol 
# Binds to fibronectin: The uteroglobulin knockout mice on the inbred C57Bl6 strain develop Goodpasture's syndrome like glomerulopathy due to fibronectin binding of IgA which might potentially be prevented by uteroglobin replacement. However contrary to the animal model claims, human genetic data might suggest that the effect may be indirect
# Uteroglobin knockout mice on the inbred 129 strain appear to have healthy phenotype (no glomerulopathy development), but show physiological differences in their responses to respiratory challenges. The phenotype exhibited by these mice are; decreased bioaccumulation of biphenyls, susceptibility and increased IL-13, and IL-6 following hyperoxic challenge, and changes in the club cell morphology. 
# Target of polychlorinated biphenyl (pcb) binding