An interstitial ectopic pregnancy is identified at 10 weeks gestation on MRI. The patient is haemodynamically stable. Compared to a tubal ectopic, which feature of interstitial ectopic pregnancy makes it particularly dangerous?
- A Higher rate of methotrexate failure due to poor vascularisation
- B Risk of rupture at a later gestational age with massive haemorrhage due to myometrial hypertrophy around it ✓
- C Invariably associated with heterotopic IUP
- D Located entirely outside the uterus, making cornuostomy impossible
Correct answer: B. Risk of rupture at a later gestational age with massive haemorrhage due to myometrial hypertrophy around it
Explanation
Interstitial (cornual) ectopic pregnancies implant in the interstitial portion of the fallopian tube within the myometrium. The surrounding myometrium allows them to grow to a larger size (often 8–16 weeks) before rupturing. When rupture occurs, the rich vascular supply of the uterine and ovarian arteries at this location causes massive, rapidly fatal haemorrhage — with mortality higher than ampullary tubal ectopics. They are richly vascularised (not poorly), not invariably associated with heterotopic IUP, and cornuostomy/cornual resection is a recognised surgical approach.
Reference: Williams Obstetrics, 26th ed.
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