Objective: We present the incidence and results of treatment of symptomatic physiologic hydronephrosis in 3,400 pregnant women. Methods: We analyzed 103 consecutive women who presented with clinical signs and symptoms related to the upper urinary system. Renal sonography, urinalysis, serum creatinine levels, white blood cell (WBC) count, and urine culture were done in all patients at first visit and repeated at least once a month until 1 month after delivery. In patients who manifested acute pyelonephritis, urinalysis, WBC count, erythrocyte sedimentation rate and C–reactive protein levels were repeated every 3 days until normalization, and urine culture as well as renal sonography were performed once a week until 1 month after delivery. Conservative measures (positioning, analgesia, antibiotics) were performed in all patients with symptomatic physiologic hydronephrosis. If the patient’s condition was refractory to medical management, drainage of the ureter with a double pigtail stent was performed. Results: Conservative measures were successful in 97 (94%) of 103 patients but 6 (6%) patients had ongoing signs and symptoms of acute pyelonephritis progressing to urosepsis. In all of them, antibiotics were continued and a double pigtail stent was placed resulting in fast regression of symptoms, curing of renal infection and progresse of the pregnancies to the term with vaginal delivery. Conclusions: Symptomatic hydronephrosis in pregnancy can be treated conservatively. If the patient’s condition is refractory to medical management, an internal drainage with double pigtail stent may be necessary.