To determine an optimal invasive intervention for renal colic patients during pregnancy after conservative treatments have been found to be unhelpful. Among the available invasive interventions, we investigated the reliability of a ureteral stent insertion, which is considered the least invasive intervention during pregnancy. Between June 2006 and February 2015, a total of 826 pregnant patients came to the emergency room or urology outpatient department, and 39 of these patients had renal colic. The mean patient age was 30.49 years. In this retrospective cohort study, the charts of the patients were reviewed to collect data that included age, symptoms, the lateralities and locations of urolithiasis, trimester, pain following treatment and pregnancy complications. Based on ultrasonography diagnoses, 13 patients had urolithiasis, and 13 patients had hydronephrosis without definite echogenicity of the ureteral calculi. Conservative treatments were successful in 25 patients. Among these treatments, antibiotics were used in 15 patients, and the remaining patients received only hydration and analgesics without antibiotics. Several urological interventions were required in 14 patients. The most common intervention was ureteral stent insertion, which was performed in 13 patients to treat hydronephrosis or urolithiasis. The patients' pain was relieved following these interventions. Only one patient received percutaneous nephrostomy due to pyonephrosis. No pregnancy complications were noted. Ureteral stent insertion is regarded as a reliable and stable first-line urological intervention for pregnant patients with renal colic following conservative treatments. Ureteral stent insertion has been found to be equally effective and safe as percutaneous nephrostomy, which is associated with complications that include bleeding and dislocation, and the inconvenience of using external drainage system.