Ectopic pregnancy

Ectopic pregnancy refers to the implantation of a fertilised ovum outside of the uterine cavity.

The overall incidence has increased over the last few decades and is currently thought to affect 1-2% of pregnancies. The risk is as high as 18% for first trimester pregnancies with bleeding 14. There is an increased incidence associated with in-vitro fertilisation (IVF) pregnancies.

The classic presentation is with abdominal pain and bleeding.  In practice, the symptoms are not necessarily severe - often there may be only mild pelvic pain and PV spotting in a patient in early pregnancy (5-9 weeks of amenorrhoea 5). Nonetheless, monitoring of haemodynamic status is crucial, as haemorrhage can be life threatening.

Locations

In the vast majority of cases, the ectopic implantation site is within a Fallopian tube.

Risk factors
Markers

Serum beta HCG levels tend to increase at a slower rate. Whereas a normal doubling rate in early pregnancy is approximately 48 hours, an increase of 50% or less in 48 hours is strongly suggestive of a non-viable (either intra- or extra-uterine) pregnancy 10. Rarely the urinary and/or serum b-HCG will be negative despite an ectopic pregnancy 12.

Serum progesterone levels are generally lower in a non-viable (including ectopic) pregnancy 6; a progesterone of 5 ng/ml or less is strongly associated with pregnancy failure, whereas in a viable pregnancy, progesterone is usually 20 ng/ml or more 5. Clearly, there is a significant grey zone. Furthermore, serum progesterone levels may take days to process. Progesterone is therefore not included in standard protocols for managing suspected ectopic pregnancy.

It is useful to know a quantitative beta HCG prior to scanning as this will guide what you expect to see. At levels <2000 IU, a normal early pregnancy may not be visible.

Ultrasound

The ultrasound exam should be performed both transabdominally and transvaginally. The transabdominal component provides a wider overview of the abdomen, whereas a transvaginal scan is important for diagnostic sensitivity.

Positive sonographic findings include:

  • uterus
    • empty uterine cavity or no evidence of intrauterine pregnancy
    • pseudogestational sac or decidual cyst: may be seen in 10-20% of ectopic pregnancies
      • current evidence suggests that one should not initiate treatment for an ectopic pregnancy in a haemodynamically stable woman on the basis of a single hCG value 10
    • decidual cast
    • thick echogenic endometrium
  • tube and ovary
    • simple adnexal cyst: 10% chance of an ectopic
    • complex extra-adnexal cyst/mass: 95% chance of a tubal ectopic (if no IUP)
    • solid hyperechoic mass is possible, but non-specific
    • tubal ring sign
      • 95% chance of a tubal ectopic if seen
      • described in 49% of ectopics and in 68% of unruptured ectopics
    • ring of fire sign: can be seen on colour Doppler in a tubal ectopic, but can also be seen in a corpus luteum
    • absence of colour Doppler flow does not exclude an ectopic
    • live extrauterine pregnancy (i.e. extra-uterine fetal cardiac activity): 100% specific, but only seen in a minority of cases
  • peritoneal cavity
    • free pelvic fluid or haemoperitoneum in the pouch of Douglas
      • the presence of free intraperitoneal fluid in the context of a positive beta HCG and empty uterus is
        • ~70% specific for an ectopic pregnancy 4
        • ~63% sensitive for ectopic pregnancy 4
        • not specific for ruptured ectopic (seen in 37% of intact tubal ectopics)
    • live pregnancy: 100% specific, but only seen in a minority of cases

In patients receiving in vitro fertilisation (IVF), it is important not to be completely reassured by the presence of a live intrauterine pregnancy 8, as there is a possibility of a coexisting ectopic pregnancy in ~1:500 (i.e. heterotopic pregnancy). In patients not receiving IVF, the risk of heterotopic pregnancy is minuscule (1:30,000).

Complications somewhat depend on the type of ectopic. General complications for a typical (tubal) ectopic pregnancy include:

Management depends on the location of the ectopic pregnancy and the patient's haemodynamic status. In general, the options are:

  • surgical: (in the case of tubal ectopics with open or laparoscopic salpingectomy or salpingotomy)
  • medical
    • methotrexate (a folate antagonist) either administered systemically or by direct ultrasound guided injection or potassium chloride (direct injection only obviously)
    • relative contraindications to methotrexate include 11:
      • rupture
      • mass >3.5 cm
      • fetal cardiac activity
      • bHCG >6000-15,000 mIU/mL
    • the gestational mass can paradoxically increase in size following methotrexate on subsequent scanning and does not necessarily imply failure of methotrexate therapy 3
  • conservative or expectant management is being recognised as an option for those ectopics where rupture has not occurred (i.e. no haemoperitoneum) and fetal demise has already taken place

The differential diagnosis of abdominal pain in a pregnant patient is broad. An ectopic pregnancy must be excluded with ultrasound. Other common diagnoses in this setting include:

The scenario of clinically suspected ectopic pregnancy that is not confirmed on ultrasound, is referred to as a pregnancy of unknown location, with the alternative possibilities being of a very early pregnancy or a completed miscarriage.

Ultrasound - obstetric
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Article information

rID: 1258
Section: Pathology
Synonyms or Alternate Spellings:
  • Ectopic pregnancies
  • Extrauterine gestation
  • Extra-uterine gestation
  • Ectopic

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Cases and figures

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    Figure 1: location of ectopics
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    Case 1
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    Ectopic pregnancy
    Case 2
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    Case 3: live adnexal ectopic
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    Transvaginal gray...
    Case 4: with a hyperechoic tubal ring
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    Case 5: live ovarian ectopic
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    Case 6: "ring of fire" sign (hypervascular ring)
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    Case 7: tubal ectopic
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    Case 8
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    Heteroechoic mass...
    Case 9
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