Acute abdominal pain in pregnant women may complicate the diagnostic process of acute abdominal pain because of anatomical and physiological changes and limitations of computed tomography examinations related to radiation exposure. Here, we present the case of a 35-year-old female in her 10th week of pregnancy who was seen in the emergency department with unilateral abdominal pain and gross hematuria. Ultrasound detected only hydronephrosis and failed to identify ureteral stones, but magnetic resonance imaging revealed a diagnosis of idiopathic renal hemorrhage and intraductal ureteral hematoma, not ureteral stones. Although magnetic resonance imaging for pregnant women has the disadvantages of prolonged scan time and difficulty in image interpretation, no harm or complications to the mother or fetus have been reported. Magnetic resonance imaging may be considered in assessing acute abdominal pain in pregnant women, especially when the diagnosis is uncertain, based on shared decision-making with the patient and assessing the clinical situation and availability.