1. Tobacco smoke contains around 4000 substances, most of which are described as toxic, and they may have an influence on the development of progeny. 2. The present studies concentrate on the measurement and calculation of indices describing the new-born's survival, rearing of pups, weight of foetuses, young animals, placenta and females in relation to different doses of tobacco smoke (carbon monoxide levels). The morphological studies of placenta, foetal and newborn lungs were done as a supplement. Biochemical placenta study was also done. 3. The results of the experiment proved that some indices for animals in groups which were passively exposed to the highest concentrations of tobacco smoke were lower, others fluctuated (4 day, 12 day and total survival) and some did not reveal any changes (rearing). Direct correlation between maternal passive exposure to tobacco smoke and the presence of acute respiratory distress syndrome symptoms in new-borns was observed. A decrease of body weight of pregnant females passively exposed to tobacco smoke was also observed. An increase of placenta-foetal factor was found. A decrease of rat weight was observed after passive exposure to tobacco smoke. 4. We concluded that there is correlation between passive exposition to tobacco smoke during pregnancy and delayed lung maturation in the offspring. Exposure of the pregnant rats to cigarette smoke increases the activity of isocitric and glucose-6-phosphate dehydrogenases in placenta.