Patients with urolithiasis and/or urinary infection during pregnancy may have obstruction of the upper urinary tract. In the presence of obstruction and urinary infection, obstructive pyelonephritis occurs, which is a life-threatening complication for both the mother and the fetus. In such cases, drainage of the kidney and upper urinary tract is indicated, as a rule, with a ureteral catheter-stent [1, 2]. Permanent drainage of the upper urinary tract by a stent may be complicated by salt encrustation and the formation of stones on proximal and distal rings. The process of stone formation progresses with increasing the duration of the stent in the urinary tract. This is facilitated by the adhesion of pathogenic microorganisms in the form of biofilms on the surface of the stent, which in turn increases the precipitation of salts and causes long-term persistence of the combined microflora. These factors make it difficult and sometimes impossible procedure for stent removal due to its increased rigidity. Researchers have shown that this process is especially rapid in pregnant women with known gestational features of mineral and bone metabolism and urine composition. Therefore, international and domestic recommendations on urology prescribe replacement/removal of ureteral stents no later than 2 months after their installation during pregnancy [1, 2]. In some cases, stone formation on the stent occurs according to an "accelerated schedule" and aggravates the course of pregnancy due to obstructive and inflammatory complications. In such situations, it is necessary to perform puncture nephrostomy and additional endourological interventions [3]. In our clinical case, female patient S., 25 years old, had a stone in the upper third of the left ureter during the first pregnancy. Fifteen (!) urological endoscopic operations were performed due to the massive deposition of salts on the stents, which made it difficult to remove or replace them (Fig. 1, a-e). Repeated drainage was indicated due to obstructive pyelonephritis, however, all installed drains after 2-3 weeks became urate petrified, which in turn was the cause of ureteral obstruction. Pregnancy in patient S. was complicated by fetal distress with negative diastolic blood flow in the umbilical cord artery, fetal heartbeat disorders: cardiotocography is of questionable type, reduction of fetal heartbeats to 90-100 per minute. At the gestational age 33-34 weeks, an emergency cesarean section was performed. The weight of the newborn girl was 1895 g, length - 44 cm, Apgar score - 7/7 points. The newborn needs treatment at the neonatal intensive care unit and then be transferred to the special unit of nursing for premature newborns. The protocol for monitoring pregnant women with ureteral stents should include regular ultrasound examinations of the urinary system and microbiological examinations of urine to prevent the above-mentioned obstructive complications. It is important to strictly follow the recommendations on the timing of removal or replacement of drains. Informed consent for publication of patient's information and images was obtained from our patient. None of the authors has a conflict of interest. Authors contribution: B.N.V. - collection, writing the text, analisis, E.I.P. - writing and correction of the text, supervision, I.G.N. - correction of the text.