Semantics and pitfalls in the diagnosis of cornual/interstitial pregnancy

OBJECTIVE(S): To clarify the respective definitions of cornual and interstitial pregnancy and to explore the difficulties in diagnosing these entities, particularly in the context of Müllerian fusion defects. DESIGN: Case study. SETTING: Community and tertiary-care hospitals. PATIENT(S): Female with recurrent pregnancy loss initially diagnosed with an interstitial pregnancy but subsequently found to have a cornual pregnancy in a bicornuate/septate uterus. INTERVENTION(S): Imaging with two-dimensional and three-dimensional ultrasound, hysterosalpingogram, serial beta-hCG measurement, administration of methotrexate and misoprostol, and aspiration and curettage. MAIN OUTCOME MEASURE(S): Measurement of beta-hCG levels and pathologic evaluation of aspiration and curettage material. RESULT(S): Correct diagnosis and eventual termination of cornual pregnancy and identification of a uterine anomaly were achieved. The process led to the development of an enhanced understanding of diagnostic modalities and their limitations with regard to the entities under discussion. CONCLUSION(S): Accurate diagnosis of an interstitial pregnancy requires that those reading and reporting ultrasounds use consistent, precise nomenclature. Clinicians must remain cognizant of the limitations of ultrasound in distinguishing cornual (intrauterine) from interstitial (ectopic) pregnancies and the influence of uterine anomalies on this distinction.