Ectopic pregnancy

Definition

Location and frequency

• Ectopic pregnancy (EP) affects approximately 1 to 2% of all pregnancies.
• Over 95% of all EPs are located in the fallopian tube, most commonly in the in the ampullary tubal section.
• The interstitial (cornual) site accounts for about 2–4% of all ectopic pregnancies.
• A rare special form is a heterotopic pregnancy, in which an ectopic pregnancy and an intrauterine pregnancy coexists.

Aetiopathogenesis

Risk factors

• An in-situ intrauterine device (IUD) reduces the absolute number of pregnancies, but if one occurs, the proportion of ectopic implantations is relatively increased.

Clinical features

Presentation and diagnostics

• The cardinal symptoms are secondary amenorrhoea, unilateral lower abdominal pain, and light spotting or bleeding.
• On examination, typical findings include cervical motion tenderness, tenderness in the pouch of Douglas, and often a unilateral, palpable adnexal mass.
• In the event of a rupture, an acute abdomen, haemodynamic instability, and, as a sign of diaphragmatic irritation, unilateral shoulder pain may occur.
• The initial diagnostic steps include checking vital signs, a pregnancy test, determination of blood group and haemoglobin, as well as quantitative hCG and vaginal ultrasound.

More facts from the study questions

• Over 95% of all ectopic pregnancies are located in the fallopian tube.
• Within the tube, the ampullary location is the most frequent.
• A rupture leads to intra-abdominal bleeding (haemoperitoneum).
• The blood can irritate the diaphragm, which can manifest as referred pain in the shoulder (phrenic sign).
• The interstitial, also known as cornual, location is less common.
• It accounts for about 2 to 4% of all ectopic pregnancies.
• An intrauterine device (IUD) very effectively reduces the absolute number of all pregnancies.
• If pregnancy does occur, the proportion of ectopic implantations relative to intrauterine ones is increased.
• A ruptured corpus luteum can also lead to haemoperitoneum and acute lower abdominal pain.
• In an ectopic pregnancy, the uterine cavity remains empty while the endometrium is hormonally stimulated.

Diagnosis

Examination procedure and indirect signs

• An important indirect sign is an empty uterine cavity with a positive pregnancy test and a thickened endometrium.

Classic adnexal findings

• The 'bagel sign' or tubal ring is a round structure with an echogenic ring and an anechoic centre, which is located separate from the ovary.
• When attempting to move the finding with the probe, the bagel sign moves independently of the ovary.
• The 'blob sign' is the most common finding and appears as an inhomogeneous mass next to the ovary.
• The 'ring of fire' on colour Doppler shows strong circular perfusion and is non-specific (also in corpus luteum).

Proof and warning signs

• The only definitive proof of an ectopic pregnancy is the extrauterine sac with embryo/yolk sac.
• This direct proof is only successful in approx. 20% of cases.
• Free fluid in the Pouch of Douglas or Morison's pouch that is echogenic (haemoperitoneum), is a warning sign.

Special forms and inconclusive findings

• In an interstitial pregnancy, the gestational sac is found eccentrically high in the fundus, surrounded by a thin myometrial strip (< 5 mm).
• A caesarean scar pregnancy is present if the gestational sac is located in the niche of the anterior lower uterine segment and there is a very thin myometrium towards the bladder exists.
• In a cervical pregnancy, the gestational sac is located below the internal os with a closed external os and can be distinguished from a cervical abortion by the differentiate by 'sliding sign'.
• An unremarkable ultrasound scan with a positive test does not rule out an ectopic pregnancy; the condition is termed a pregnancy of unknown location.

Beta-hCG trend

• In serum, beta-hCG is detectable approximately 8–9 days after ovulation, whereas urine tests only become reliable after a missed period.
• In a viable early pregnancy, the level rises by at least ≥ 50% in 48 h.
• The peak is reached around the 8th to 10th week, after which the rise flattens.
• An insufficient rise or an overly slow decline suggests a non-viable or ectopic pregnancy, but does not prove its location.

Typical imaging findings

• Ultrasound: Beside the uterus and separate from the ovary lies a round structure with an echogenic ring-like rim and a more hypoechoic centre (tubal ring, bagel sign). The uterine cavity contains no gestational sac; the endometrium is thickened and decidualised.
• Ultrasound: Beside the uterus lies a ring-shaped structure with an echogenic rim. Colour Doppler shows a strong, almost closed vascular ring around it, while the uterine cavity contains no gestational sac.

Keep learning in the app

Further reading (selection)

1. StatPearls: Ectopic Pregnancy (NCBI Bookshelf)
2. StatPearls: Ectopic Pregnancy, Ultrasound (NCBI Bookshelf)
3. DocCheck Flexikon, Extrauteringravidität
4. DocCheck Flexikon, Humanes Choriongonadotropin

Cross-references