Appendectomy is the most common non-gynecologic surgery performed during pregnancy. Little data exist on the accuracy of imaging studies in the diagnosis of appendicitis in pregnancy. The objective of this study was to evaluate the probability of ultrasound and computed tomography (CT) scan in diagnosing appendicitis in pregnancy, as reflected in the negative appendectomy rate. We retrospectively reviewed the charts of 86 pregnant women who underwent an appendectomy between January 1, 1997 and January 1, 2006. Patients were divided into three groups: clinical evaluation, ultrasound, and ultrasound followed by a CT scan. The clinical evaluation group had 13 patients, with a negative appendectomy rate of 54% (7/13). Fifty-five patients underwent an ultrasound alone, with a negative appendectomy rate 36% (20/55). In the ultrasound/CT group (n=13), the negative appendectomy rate was 8% (1/13). There was a significant reduction in the negative appendectomy rate in the ultrasound/CT scan group compared to clinical evaluation group (54 vs 8%, p<0.05). This reduction was not achieved in the ultrasound group when compared to the clinical evaluation group or the ultrasound/CT group (p=0.05). A significant reduction was achieved when the ultrasound/CT group was compared to the patients in the ultrasound only group who had a normal or inconclusive ultrasound (p<0.05). Our data documents a very high negative appendectomy rate in the pregnant patient. We recommend an ultrasound followed by a CT scan in patients with a normal or inconclusive ultrasound.