Objective To evaluate the effects of ethanol–water (80:20) extract of Marrubium vulgare (M. vulgare) on the hematological parameters, macroscopic and histological aspects of the uterus and fetus in non-pregnant and pregnant rats. Methods Female rats were divided into 4 equal groups (n = 9), group N (normal rats) and group G (pregnant rats) considered as control groups, group NE (normal rats treated with the ethanol–water (80:20, v/v) extract of M. vulgare) and group GE (pregnant rats treated with the extract). The ethanol–water (80:20) plant extract was administered in a single daily dose 1 g/kg at the morning, during 19 d. On the 19 day of the experiment, animals were sacrificed, the uterus and fetuses were removed for the morphological and histological studies and the blood was collected in EDTA tubes for the measurement of hematological parameters with the use of an automate ‘HORIBA ABX Micros 60 Hematology Analyzer’. Results Our results showed, in group NE and GE, a significant decrease on hematological parameters: red blood cells (NE: 18.6%; GE: 38.4%), hematocrit (NE: 13.8%; GE: 20.4%), hemoglobin (NE: 12.1%; GE: 8.3%) and mean corpuscular volume (NE: 6.4%; GE: 2%) with P more less a 0.05. Indeed, the extract of M. vulgare caused a significant decrease on the mean implantations of fetuses (82.5%, P < 0.001) and their size (47.2%, P < 0.01). As for the macroscopic and histological appearance of uterus, our data showed no change in normal treated rats. In contrast, the treated pregnant rats showed a severe histological change characterized by the existence of location of stopped gestation. Furthermore, it was also found in the uterus of these rat lyses placental and embryo tissue. Conclusions All these results support the hypothesis of an abortifacient effect of M. vulgare.