Purpose <p>To identify factors contributing to misdiagnosis of interstitial ectopic pregnancy (IEP).</p> Methods <p>Retrospective chart review identified patients who presented to Boston Medical Center with suspected and/or true IEP from January 1, 2012 to April 30, 2019. Final diagnoses identified two IEP diagnosis groups: correct initial diagnosis and incorrect initial diagnosis. Data collected included age, gravidity, parity, body mass index (BMI), estimated gestational age, anatomic anomalies of the reproductive tract, smoking status, and history of pelvic surgery, sexually transmitted infections, pelvic inflammatory disease, or adnexal lesions. Continuous variables were analyzed using analysis of covariance and unpaired t-tests. Fisher’s exact tests were used for discrete variables.</p> Results <p>Of 53 patients with suspected and/or true IEP, 15 (28%) were correctly diagnosed at initial presentation while 38 (72%) were initially incorrectly diagnosed. Patient age was significantly associated with diagnostic group (<i>p</i> = 0.04). Patients in the correctly diagnosed group (Mean ± SD = 35.1 ± 4.2) were significantly older than those incorrectly diagnosed (Mean ± SD = 30.4 ± 4.2) when controlled for gravidity. In univariate analysis, gravidity was associated with diagnostic group, but this association was not significant when controlled for age. Parity demonstrated a similar trend as gravidity but also did not reach significance. Other variables analyzed were not significantly associated with accuracy of initial diagnosis.</p> Conclusion <p>Younger women are more likely to have an incorrect initial diagnosis of IEP at presentation to care. Anecdotally, higher tolerance of invasive imaging procedures by older patients with reproductive experience may result in increased accuracy of transvaginal ultrasound examination.</p> Graphical abstract <p></p>