Objective: The aim of the study is to evaluate maternal serum atrial natriuretic peptide (ANP) and brain-type natriuretic peptide (BNP) levels in patients with getational diabetes mellitus compared with a control group.Methods: We have measured maternal serum ANP and BNP levels in 35 otherwise healthy and 45 gestational diabetic women between gestational week 24 and 28 referred to our unit in a cross-sectional study. Independent samples t-test or the Mann-Whitney U-test was used for comparison of two groups where appropriate.Results: Mean maternal serum homeostasis model assessment of insulin resistance (HOMA-IR), HbA1c, fasting glucose and insulin levels in gestational diabetes mellitus (GDM) group were significantly higher than the control group (p<0.01). Mean maternal serum ANP and BNP levels of women with GDM were significantly lower than the control group (12.99.9 versus 34.8 +/- 16.9pg/ml, p<0.001; 416.6 +/- 209.7 versus 629.7 +/- 162.2mg/dl, p<0.001, respectively). Maternal serum ANP and BNP levels were negatively correlated with insulin levels, HbA1c and HOMA-IR values (p<0.05).Conclusions: Maternal serum ANP and BNP levels are significantly lower in patients with GDM. These biomarkers might be valuable in clinical setting for identifying high-risk women for developing diabetes during pregnancy