Appendix 3: Ectopic pregnancy location

Tubal ectopic

  • Most common
  • Adnexal mass ± gestational sac
  • May demonstrate peripheral vascularity
  • Ectopic angle is the most common site (between the uterus and ovary).

Non-tubal ectopic pregnancy

  • Interstitial/cornual ectopic: mass or gestational sac in the cornual region of the uterus, outside the endometrial cavity
  • Scar ectopic: mass or gestational sac related to the caesarean section scar
  • Cervical ectopic: mass or gestational sac within the endocervical canal
  • Ovarian ectopic: mass or gestational sac within the ovary. This is a rare condition (less than 1 percent of ectopics) and needs to be differentiated from the much more common corpus luteum (see below)
  • Abdominal and intramural ectopics are rare.

Heterotopic pregnancy

  • A rare condition of co-existing intrauterine and ectopic pregnancy
  • Rare (0.6–2.5 per 10,000 pregnancies)
  • Increased incidence in women undergoing IVF or ovulation induction
  • If suspected sonographically, then specialist opinion is required.

Corpus luteum of pregnancy

  • Seen within the ovary in early pregnancy
  • May be single or multiple
  • Appearances may be those of a thin- or thick-walled cyst or solid isoechoic nodule with peripheral ring vascularity
  • An exophytic corpus luteum on the periphery or surface of the ovary may mimic an ectopic pregnancy. It may be difficult to differentiate a corpus luteum from an ectopic pregnancy.

Helpful sonographic features include:

  • no internal yolk sac or embryo
  • isoechoic to the ovary
  • moves with the ovary on probe pressure.

If there is an empty uterus and indeterminate ultrasound findings, a follow-up scan should be recommended (in 5–7 days, or earlier if there is interval clinical concern regarding ectopic pregnancy). An ectopic pregnancy or a normal intrauterine pregnancy may often become visible on the follow-up scan.

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