The placenta is an important target organ for toxic actions of many of chemicals. So, to examine the effects of phenol on placental microscopic changes, 40 pregnant mice were divided into one control and three experimental groups. The control mice received distilled water by gavage method between 6 to 16 pregnancy days, and the three experimental groups received concentrations of 80, 180, and 320 mg/kg phenol for the same time and method, respectively. At the 17th day of pregnancy, all of the mice were sacrificed, their placentas collected, and all of morphological and structural changes recorded. A significant increase in placental weight and diameter and in the ratio of placental to fetal weight was found in treated groups in comparison with the control mice (p < 0.05). Histological changes included a decrease in size of the labyrinth zone and an increase in size of the junctional zone of placenta. An increase in the number and size of spongiotrophoblasts and trophoblastic giant cells was also seen. Furthermore, an increase in thickness of the basement membrane between III trophoblastic layer and fetal endothelial capillary, an increase in diameter of the labyrinth interhemal membrane (LIM), formation of intracytoplasmic vacuoles in II and III trophoblastic layers, and formation of electron-lucent endothelial intracytoplasmic droplets in LIM were seen. Morphological and structural changes observed in placental tissue indicated a significant injury. So it might be concluded that treatment with phenol can induce harmful effects on the placenta.
