In metabolism of homocysteine several enzymes and vitamin cofactors are involves. Genetic abnormalities in these enzymes or nutritional deficiency vitamins, especially of folate may lead to hyperhomocysteinemia, a known risk factor for some pregnancy complications. High maternal homocysteine and low folate levels correlate with low birth weight. Maternal smoking affected significantly total homocysteine concentration in infants. Studies in this area are still scarce and report on limited number of patients. The aim of our study was to assess serum folate and total homocysteine (tHcy) concentrations in smoking pregnant women and in their newborn infants as compared with nonsmoking. The study consisted of 57 pregnant women, who qualified into two groups: smoking (n=28) and nonsmoking (n=29). The serum concentrations of folate were determined by electrochemiluninescent method and tHcy by fluorescence polarization immunoassay. We shown, that serum homocysteine concentrations were significantly higher in smoking as compared with nonsmoking pregnant women (p<0.05) as well as in umbilical cord blood of their newborns (p<0.001). The folate levels were comparable in serum both groups of mothers, but in infants born to smoking women were lower by 20%. In addition, the maternal serum levels of homocysteine and folate showed a significant positive correlation's with these parameters in newborns. Average birth weight infants born to smoking mother was significantly lower than nonsmoking cigarettes (p<0.05). It seems that tobacco smoking during pregnancy affected folate and homocysteine levels in serum of mothers and their infants. Smoking exposure is also associate with reduced birth weight.