Carisoprodol is a common muscle relaxant indicated as adjunctive therapy in acute, painful musculoskeletal cases. This current study aimed to investigate the histopathological, histochemical and immunohistochemical effects in the lung tissue of the pregnant rats and their fetuses after carisoprodol treatment. The present study was applied on twenty seven pregnant female rats and they were randomly divided into three groups (nine pregnant female rats in each group). Rats of the first (control) group were administered oral doses of distilled water. Rats of the second (S1) and third groups (S2) were administered oral doses of carisoprodol in the distilled water equivalent to 10.8 mg and 21.6 mg/100g body weight/day respectively for fifteen days from the six to the twenty day of gestation. Several histopathological, histochemical and some immunohistochemical changes were studied to detect the pathological changes. Maternal and fetal pulmonary tissues of both treated groups showed numerous degenerative changes post-treatment with carisoprodol, the severity of these changes was more obvious in the fetal lung tissue of both groups. Also, carisoprodol treated rats showed a marked increase in caspase-3 content in the maternal and fetal pulmonary tissues. Treatment of pregnant rats with carisoprodol drug led to numerous dystrophic changes in both maternal and fetal lung tissues.