Objective: We aimed to identify a noninvasive marker for clinically significant fetal uropathies. To achieve this aim, we detected TGF (transforming growth factor)-1 serum level which rises in neonatal hydronephrosis, in pregnant patients with fetal hydronephrosis.Materials and methods: We evaluated 44 patients, all of whom were pregnant and had a gestational age between 20 and 30 weeks. Twenty-two patients had normal maternal renal ultrasound imaging and had a fetus with fetal hydronephrosis (Group A). The remaining twenty-two patients had normal maternal and fetal renal ultrasound imaging (Group B). The maternal serum levels of TGF-1 were measured with a sandwich enzyme-linked immunosorbent assay (ELISA) using a commercially available kit.Results: The median value for the study group was 55.90pg/mL (9.67574.45) and for the control group was 59.49pg/mL (12.49 +/- 402.04). There was no statistical difference in serum TGF-1 levels between the groups (p=0.769 - Mann-Whitney U test). In the study group, the diameter of the right renal pelvis was 5.7mm (5.1-8.9mm), while the diameter of left renal pelvis was 5.75mm (5.3-10.04mm).Conclusion: In our study, the circulating TGF-1 levels were not statistically different in the fetal hydronephrosis group when compared to the controls. According to our study, TGF-1 is not useful in the detection and follow-up of fetal hydronephrosis. We therefore require further studies involving larger groups with moderate or severe fetal hydronephrosis to detect the usefulness of the serum levels of TGF-1 in pregnant women with fetal hydronephrosis.