placental intravillous accumulation of sulfated mucosubstances a reevaluation of socalled hydropic degeneration of villi a histochemical study was performed on 46 placentas showing socalled hydropic degeneration of villi the 46 cases included early abortuses 35 cases incomplete moles four cases and complete hydatidiform moles seven cases all the specimens showed diffuse positive staining of the distended villous stroma with alcian blue at ph 12 and 25 in the areas containing hydropic changes the alcian blue positivity was abolished following digestion with hyaluronidase these findings indicate that socalled hydropic degeneration of villi represents an intravillous accumulation of strongly sulfated mucosubstances rather than the result of the accumulation of water the intravillous accumulation of mucosubstances most likely represents a nonspecific stromal reaction of the connective tissue of the placenta to a variety of noxious stimuli this finding may have some bearing on the interpretation of the physiologic mechanisms involved in placental villous distention which has been largely centered in the past on the premise that the villous swelling was related to hemodynamic alterations caused by the accumulation of water