Placental Changes Following Fetal Death in Rats

The effect of the death or removal of the fetuses at the middle and late stages of pregnancy to the placenta in rats is studied. Either death or removal of the fetuses during pregnancy brought rapid degeneration of all elements of the placenta, first in the yolk sac followed by labyrinth and junctional zone leading into ischemic necrosis secondary to the thrombosis of the maternal blood vessels supplying the placenta. Trophoblasts in the junctional zone survived for a short period of time, but no evidence of abnormal or continuous proliferation of them was noted. Shortly after the death or removal of fetuses cystic degeneration in the junctional zone was observed, but no definite evidence of mole like change was noted. Findings of periodic acid Schiff's reaction, methyl-green pyronine staining and Feulgen reaction in the normal and degenerating placentas are described. The circulatory factors and structural differences between the rat and human placentas are discussed to account for differences observed in the placental changes following the death of fetuses in rats from those of human.