It is commonly known, that tobacco smoking during pregnancy has negative influence on child birth mass. Also in polish population neonates of smoking mothers are frequently born with lower body mass and are smaller. Purpose of this study was to estimate the percentage of women smoking during pregnancy and its relation to body mass of newborns. Research was made on the basis of standardized survey questionnaire done in the group of 20320 mothers. Women were divided into non-smoking and smoking before conception and during pregnancy. Questions concerned also intensity of smoking and body mass of a child. Among of participants 41.5% were in smokers group with tendency to decrease in the course of pregnancy. However even in 3-rd trimester percentage of smoking mothers was high. Body mass of newborns of smokers was lower than in group of abstinent and was related to intensity of smoking. In the light of these results some more intensive prophylactic and education actions are needed.