The target of this study was to investigate levels of brain natriuretic peptide (BNP) in pregnant women with heart failure associated with congenital heart diseases. We examined 22 pregnant women with non-operated congenital heart diseases (1 group) and HF of I–II stage, 26 pregnant women with previously corrected congenital heart diseases (2 group) and HF of I–II stage. A control group included 20 pregnant women without significant extragenital abnormalities and with physiological pregnancy. During the 2nd trimester of pregnancy we observed increase of the BNP circulating level in women with non-corrected and previously corrected congenital heart diseases as compared to pregnant women of the control group of similar age. Moreover, the highest levels of this peptide were determined in group with non-corrected CHD. During the 3rd trimester, opposite to women with previously corrected CHD, women with non-corrected CHD experienced significant (by 42 %) increase of plasma BNP level. The highest values were observed in subgroup of women with non-corrected CHD who had a need of early delivery due to progression of heart failure. The obtained data provide basis for research aimed at determination of BNP role in prediction of maternal and perinatal complications of women with CHD.