Background & objectives: Cyclophosphamide is one of the common drugs used for cancer treatment. Cyclophosphamide affects the placenta and it is teratogenic in pregnant women. The purpose of this study was to evaluate the protective effects of Mesna and Galbanum essential oil concurrent administration against cyclophosphamide toxicity in rat placenta tissue.

Methods: 22 pregnant female rats were randomly divided into 3 groups: (1) control (normal saline, n=7 rats), (2) cyclophosphamide (15mg/kg, n=7 rats), (3) cyclophosphamide (15mg/kg), Mesna (100mg/kg) and Galbanum (200mg/kg, n=8 rats). Medications were administered intraperitoneally on the 13th day of pregnancy. Then, rats were sacrificed on the 20^th day of pregnancy. The placenta was separated and fixed after macroscopic evaluation. 5 µm tissue sections were prepared, stained and studied by light microscopy.

Results: Cyclophosphamide reduced the placental weight, thickness and the length of the small and large diameters. Histologically, it reduced the thickness of the labyrinth and basal layers, caused necrosis and congestion in these layers, reduced giant cells numbers and caused their nuclear shrinkage (p<0.05). Mesna and Galbanum oil had no effect on placental morphometry rather than cyclophosphamide (p>0.05) but histologically it could increase the labyrinth and basal layers thickness and also the giant cells numbers (p<0.05). It could also prevent nuclear shrinkage, giant cells and spongiotrophoblasts necrosis in the basal layer and reduce congestion in the labyrinth layer (p<0.05).

Conclusion: Mesna and Galbanum oil preserved the placenta of pregnant rat against toxic effects of cyclophosphamide probably by its antioxidant features and free radicals deletion.