In interstitial (cornual) ectopic pregnancy, which criterion on ultrasound differentiates it from an intrauterine pregnancy in the cornual region?

• A Gestational sac located more than 1 cm from the lateral uterine wall with an incomplete myometrial mantle <5 mm surrounding it ✓
• B Gestational sac identified separately from the endometrial stripe with an empty uterus
• C Presence of fetal cardiac activity within the interstitial segment
• D Absence of a 'double decidual sac sign' within the uterine cavity

Explanation

Timor-Tritsch criteria for interstitial ectopic pregnancy on transvaginal ultrasound: (1) empty uterine cavity, (2) gestational sac visualised separately from the endometrium, (3) gestational sac located more than 1 cm from the lateral wall of the uterine cavity, and (4) a thin (<5 mm) or absent myometrial mantle surrounding the gestational sac. The myometrial mantle criterion (<5 mm) is the most specific, distinguishing cornual implantation from an eccentric intrauterine pregnancy. Interstitial ectopics have a rupture risk at later gestational age (8–16 weeks) due to the distensible interstitial myometrium, making early accurate diagnosis critical.

Reference: Williams Obstetrics, 26th ed.

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Written and medically reviewed by the StethoPrep medical team.