The present study examined the progression of fetal pyelectasis detected in patients during antenatal period and its relationship to postnatal urinary tract pathology. Methods: Medical records of 10 patients in whom isolated fetal pyelectasis (defined as anteroposterior [AP] diameter of renal pelvis of 5 mm or greater in the second trimester and 7 mm or greater in the third trimester) was detected in prenatal sonographic examination at perinatology clinic between January 2013 and August 2014 were retrospectively reviewed. Fetuses with additional congenital anomalies or aneuploidy were excluded. Results: Nine fetuses were male and 1 was female. Fetal renal pelvis AP diameter was <10 mm in 5 (50%), 10-15 mm in 3 (30%), and >15 mm in 2 patients (20%). Six patients (60%) had unilateral and 4 (40%) had bilateral pyelectasis. Progression of pyelectasis in those 4 patients was followed during pregnancy. After birth, ultrasonographic (US) findings of ureteropelvic junction stenosis (UPJ) (n=1), urethrocele (n=1), vesicoureteral reflux (VUR) (n=1), and posterior urethral valves (PUV) and VUR (n=1). Conclusion: Serial US examinations are important in follow-up of patient with fetal pyelectasis. Progressive and bilateral pyelectasis may be predictive of postnatal uropathy.