Second Trimester Interstitial Ectopic Pregnancy.

Background and Clinical Significance: Interstitial ectopic pregnancy is a rare but potentially life-threatening type of ectopic gestation that carries high risk of rupture and hemorrhage due to its vascular location and predisposition for delayed presentation. Case Presentation: We present a 33-year-old female with acute abdominal pain and elevated β-hCG, with transvaginal ultrasound demonstrating a live left adnexa ectopic pregnancy dated at approximately 14 weeks. MRI confirmed the gestational sac as tubal ectopic, but poorly localized within the interstitial fallopian tube. Exploratory laparoscopy revealed the gestational sac mainly in the interstitial left fallopian tube without rupture or distal involvement. Conclusions: This case demonstrates absent classic imaging findings associated with tubal, interstitial, and ovarian ectopic gestations including tubal ring sign, interstitial line sign, endo-myometrial mantle measurement, or claw sign due to location and advanced gestational age. Familiarity with these challenges and recognition that interstitial ectopic pregnancy may present atypically are important for timely recognition and management.