ectopic pregnancy

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

Epidemiology

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 . There is an increased incidence associated with in-vitro fertilisation pregnancies.

Clinical presentation

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 spotting in early pregnancy (5-9 weeks of amenorrhea ). Nonetheless, monitoring of hemodynamic status is crucial, as hemorrhage can be life-threatening.

Pathology

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 extrauterine) pregnancy . Rarely the urinary and/or serum b-HCG will be negative despite an ectopic pregnancy .

Serum progesterone levels are generally lower in a non-viable (including ectopic) pregnancy ; 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 . 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 the suspected ectopic pregnancy.

Radiographic features

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.

The most reliable sign of ectopic pregnancy is the visualization of an extra-uterine gestation, but this is not seen in 15-35% of ectopic pregnancies .

Ultrasound

The ultrasound exam should be performed both transabdominal 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
    • an empty uterine cavity or no evidence of an 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 ectopic pregnancy in a haemodynamically stable woman on the basis of a single hCG value
    • 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 color Doppler in a tubal ectopic, but can also be seen in a corpus luteum
    • an absence of color 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 hemoperitoneum in the pouch of Douglas
      • the presence of free intraperitoneal fluid in the context of a positive beta HCG and the empty uterus is
        • ~70% specific for an ectopic pregnancy
        • ~63% sensitive for ectopic pregnancy
        • not specific for ruptured ectopic (seen in 37% of intact tubal ectopics)
    • free fluid in the hepatorenal recess
      • interrogation of the right upper quadrant for free fluid reduces time to diagnosis
      • free fluid in Morison's pouch in the context of an ectopic pregnancy is highly suggestive that operative management will be necessary
    • 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 , as there is a possibility of a coexisting ectopic pregnancy in ~1-3:100 (i.e. heterotopic pregnancy). In patients not receiving IVF, the risk of heterotopic pregnancy is minuscule (1:30,000).

Complications

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

Treatment and prognosis

Management depends on the location of the ectopic pregnancy and the patient's hemodynamic 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
    • relative contraindications to methotrexate include :
      • 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
    • potassium chloride (via ultrasound-guided direct injection only)
  • conservative or expectant management is being recognized as an option for those ectopics where rupture has not occurred (i.e. no hemoperitoneum) and fetal demise has already taken place

Differential diagnosis

The differential diagnosis of abdominal pain in a pregnant patient is broad. An ectopic pregnancy must be excluded by 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 very early pregnancy or a completed miscarriage.