Diagnostic Terminology and Clinical Practice in Interstitial Ectopic Pregnancy: A Five-Year Clinical Audit

Background Interstitial ectopic pregnancy is rare and carries risks of rupture and severe haemorrhage. Accurate terminology is important because interstitial and cornual pregnancy are often used interchangeably despite representing distinct implantation sites. The primary objective of this five-year audit was to assess compliance with anatomically precise diagnostic terminology. Secondary objectives evaluated ultrasound assessment, escalation of diagnostically uncertain findings, and documented individualisation of management. Methods We retrospectively audited confirmed cases diagnosed between October 2020 and December 2025. Cases identified from Early Pregnancy Assessment Unit clinical and ultrasound records were verified against recognised diagnostic criteria. Five predefined criteria based on the National Institute for Health and Care Excellence (NICE), Royal College of Obstetricians and Gynaecologists (RCOG), and European Society of Human Reproduction and Embryology (ESHRE) guidance assessed transvaginal ultrasonography, compatible anatomical features, escalation of uncertainty, precise terminology in the final ultrasound conclusion, and individualised management. The target was 100% for each applicable criterion. Cases were classified as compliant, non-compliant, or not assessable and analysed descriptively. Results Five cases were identified. All patients underwent transvaginal ultrasonography, with reports documenting anatomical findings compatible with interstitial ectopic pregnancy. Across the five reports, these included an empty uterine cavity, a laterally located gestational sac, a thin surrounding myometrial mantle, and an interstitial line sign. Diagnosis was established on the first scan in three cases, while two diagnostically uncertain cases were confirmed following repeat assessment and lead-sonographer review. All pregnancies were diagnosed before rupture and before eight weeks' gestation. However, all final ultrasound conclusions used the term confirmed cornual ectopic pregnancy, resulting in 0% compliance with anatomically precise terminology. Management was individualised and included methotrexate, hysteroscopic resection, and surgery initiated laparoscopically. No major complications were recorded, and all hospital stays were two days or fewer. Conclusions The principal finding of this five-case retrospective audit was 0% compliance with anatomically precise terminology: all final ultrasound conclusions used the term cornual ectopic pregnancy despite imaging findings compatible with interstitial ectopic pregnancy. This represents a terminology and documentation gap rather than evidence of deficient diagnostic recognition or clinical management. Conversely, compliance was 100% for transvaginal ultrasound assessment, documentation of compatible anatomical features, escalation of diagnostically uncertain findings, and documented individualisation of management. Favourable short-term outcomes were descriptive observations and do not demonstrate the effectiveness or superiority of the diagnostic pathway or any management strategy. Standardised anatomical nomenclature may improve clinical communication, documentation quality, coding accuracy, audit reliability, and future research reporting. Educational initiatives and standardised reporting templates should reinforce the distinction between interstitial, cornual, and angular pregnancies, with re-audit recommended following improvement measures are implemented.