Background: Ureteroscopy is widely applied in pregnant women with renal colic, but such patients are easy to experience uterine contraction after ureteroscopy, There are many factors which may result to uterine contraction, this study aims to explore the risk factors of uterine contraction triggered by ureteroscopy in pregnant women with renal colic. Methods: 101 pregnant women were retrospectively analyzed, all patients were hospitalized because of severe renal colic. All patients received ureteroscopy during which double J catheters were inserted into ureters for drainage. Patients received medical treatment individually according to their condition and the uterine contractions were detected by EHG within 12 hours after operation. Patients were classified as group A (uterine contraction, n=46) and group B (no uterine contraction, n=55) according to the presence or absence of continuously regular uterine contraction. Clinical characteristics were collected for further analysis, including history of deliveries, anesthesia methods, application of phloroglucinol or not, surgical time, Oxygen inhalation or not, pain relief or not after surgery, systemic inflammatory response syndrome(SIRS) occurred or not. A binary logistic regression analysis model was established to explore whether such clinical characteristics were relevant to uterine contraction after ureteroscopy. Results: The incidence of continuously regular uterine contraction occurred within 12 hours after ureteroscopy in pregnant women was 45.54%, and the presence of uterine contraction was related to the following factors(P<0.05): history of deliveries(primipara versus multipara)(OR=6.593, 95%CI 2.231-19.490), surgical time(each quarter additional)(OR=2.385, 95%CI 1.342-4.238), application of phloroglucinol(yes versus not)(OR=6.959, 95%CI 1.416-34.194), pain relief after surgery(yes versus not)(OR=6.707, 95%CI 1.978-22.738), SIRS occurred after surgery(yes versus not)(OR=0.099, 95%CI 0.014-0.713). Conclusion: Continuously regular uterine contraction is easy to occur within 12 hours after ureteroscopy in pregnant women. SIRS occurred after surgery is a risk factor for uterine contraction; on the contrary, no history of childbirth, shorter surgical time, application of phloroglucinol, pain relief after surgery are protective factors.