Objective The objective of this study was to identify clinical factors predictive of appendicitis in pregnant women and associated obstetric outcomes. Study Design We performed a single-center, retrospective cohort study of pregnant women who underwent magnetic resonance imaging for suspected appendicitis from 2007 to 2012. Rates and odds of appendicitis based on presenting signs and symptoms were estimated. We also estimated rates and odds of adverse obstetric outcomes among women with a diagnosis of appendicitis. Results Of 171 pregnant women evaluated, 14 (8.2%) had pathology-confirmed appendicitis. White blood cell (WBC) count on admission was moderately predictive of appendicitis (area under the receiver operating characteristic curve, 0.74). A WBC count > 18,000 made the diagnosis of appendicitis more than 10 times more likely (adjusted odds ratio, 10.51; 95% confidence interval, 1.67-43.1). Of 127 women with complete pregnancy follow-up, women with appendicitis had a higher rate of pregnancy loss < 20 weeks (2/13 [15.4%] vs. 3/104 [2.9%], p < 0.01) and < 24 weeks (3/13 [23.1%] vs. 4/104 [3.8%]) than those without appendicitis. Appendicitis diagnosed in the first trimester was associated with increased risk of pregnancy loss < 24 weeks. Conclusion WBC count > 18,000 on admission is significantly associated with appendicitis in pregnant women undergoing evaluation for appendicitis. Appendicitis during the first trimester of pregnancy is associated with previable pregnancy loss.