Ectopic Pregnancy

Implantation of the blastocyst anywhere outside the endometrial cavity of the uterus. It is the leading cause of maternal death in the first trimester and a perennial NEET PG favourite — examiners love vignettes on the discriminatory zone, methotrexate eligibility, and salpingostomy versus salpingectomy.

Definition & Classification

An ectopic (extrauterine) pregnancy is one in which the fertilised ovum implants outside the uterine endometrial lining. The overall incidence is roughly 1–2% of all pregnancies, rising sharply in assisted reproduction and in women with prior tubal disease.

By site of implantation:

Site	Approx. frequency	Key point
Ampulla of fallopian tube	~70% (commonest overall)	Most common single site
Isthmus	~12%	Ruptures earliest (narrowest, least distensible)
Fimbria	~11%	May abort out of the fimbrial end (tubal abortion)
Interstitial / cornual	~2–3%	Ruptures late (8–16 wk) but causes catastrophic haemorrhage
Ovarian	~1–3%	Spiegelberg criteria; mistaken for haemorrhagic cyst
Cervical	<1%	Painless bleeding; risk of massive haemorrhage
Caesarean scar	rising	Implantation in previous LSCS scar niche
Abdominal	rare	Can rarely reach term; high mortality

High-yield: The ampulla is the commonest site overall, but the isthmus ruptures earliest because it is the narrowest and least distensible segment. The interstitial/cornual ectopic presents late and bleeds the most.

A heterotopic pregnancy is the coexistence of an intrauterine and an extrauterine gestation — classically rare (1 in 30,000) but markedly increased after IVF/ART (up to 1 in 100). Do not be falsely reassured by an intrauterine sac in an ART patient with adnexal pain.

Etiology & Risk Factors

Anything that delays or obstructs the transport of the fertilised ovum down the tube predisposes to tubal implantation.

Risk factor	Mechanism / Note
Previous ectopic pregnancy	Strongest risk factor (recurrence ~10–15%)
Pelvic inflammatory disease (PID)	Chlamydia, gonorrhoea → ciliary damage, adhesions
Prior tubal surgery / sterilisation failure	Especially failed tubal ligation, reversal
Assisted reproduction (IVF/ovulation induction)	Higher heterotopic risk
Intrauterine contraceptive device (IUCD)	If pregnancy occurs with IUCD/LNG-IUS, more likely to be ectopic
Smoking	Dose-dependent ciliary dysfunction
Endometriosis, tubal pathology	Distorted anatomy
Increasing maternal age, prior abortion	Minor risk
DES exposure (historical)	Tubal abnormalities

High-yield: A previous ectopic pregnancy is the single strongest risk factor. An IUCD reduces the absolute risk of all pregnancies but, if a pregnancy occurs in a woman with an IUCD, the proportion that is ectopic is higher.

Pathophysiology

The tubal wall lacks a proper decidual layer and submucosa, so trophoblast invades the muscularis and erodes vessels. The conceptus may (1) tubal abort out of the fimbrial end, (2) undergo tubal rupture with intraperitoneal bleeding, or (3) regress (spontaneous resolution). Erosion of vessels produces haemoperitoneum, the cause of shock.

Clinical Features

The classic triad of a ruptured tubal ectopic: amenorrhoea + abdominal pain + vaginal bleeding in a woman of reproductive age.

• Amenorrhoea: typically 6–8 weeks; sometimes the patient interprets the abnormal bleeding as a delayed period.
• Pain: lower abdominal/pelvic, may be colicky then constant; shoulder-tip pain (referred via the phrenic nerve from diaphragmatic irritation by blood) suggests significant haemoperitoneum.
• Bleeding: scanty, dark "prune-juice" spotting from decidual breakdown.

On examination:

• Pallor, tachycardia, hypotension (if ruptured) — out of proportion to visible blood loss.
• Cervical motion tenderness ("cervical excitation"), adnexal tenderness/mass, fullness in the pouch of Douglas.
• Cullen's sign (periumbilical bruising) may rarely appear with large haemoperitoneum.

High-yield — Spalding's triad is the clinical triad classically asked: amenorrhoea, irregular vaginal bleeding, and lower abdominal pain. (Do not confuse with Spalding's sign of intrauterine fetal death — overlapping skull bones on X-ray; examiners use this confusion to trick you.)

A ruptured ectopic with collapse may present with abdominal distension, guarding, and a doughy/boggy feel — the so-called "acute abdomen of the reproductive-age woman." Always do a urine pregnancy test in any such patient.

Diagnosis & Investigation of Choice

The diagnostic workhorse is the combination of serum β-hCG and transvaginal ultrasound (TVS).

1. Urine/serum β-hCG

A positive pregnancy test in a woman with pain/bleeding is ectopic until proven otherwise. Serum β-hCG is then quantified and trended.

2. The discriminatory zone

The discriminatory zone is the serum β-hCG level above which a normal intrauterine pregnancy (IUP) should be visible on TVS.

High-yield: Discriminatory zone = ~1500–2000 mIU/mL (TVS) [~6000–6500 mIU/mL for transabdominal scan]. If β-hCG is above this level and no intrauterine gestational sac is seen on TVS, strongly suspect an ectopic pregnancy.

3. β-hCG trends (when below the discriminatory zone / pregnancy of unknown location)

• Normal IUP: β-hCG rises by ≥ 53–66% over 48 hours (classically "doubles in ~48 h").
• Ectopic / abnormal pregnancy: sub-optimal rise or a plateau.
• Miscarriage: falling levels.

Stepwise approach to suspected ectopic: Positive UPT → quantitative serum β-hCG → TVS → (sac seen in uterus?) → Yes: IUP (consider heterotopic only if ART/adnexal mass) · No, and β-hCG > discriminatory zone: treat as ectopic · No, and β-hCG < discriminatory zone: repeat β-hCG at 48 h and rescan ("pregnancy of unknown location").

4. Ultrasound findings

• "Bagel"/"tubal ring" sign: echogenic ring around the gestational sac in the adnexa — the most specific TVS finding.
• "Blob sign": inhomogeneous adnexal mass separate from the ovary.
• Pseudo-gestational sac in the uterine cavity (decidual reaction with fluid) — beware mistaking for true IUP (true sac is eccentric with double decidual sign / yolk sac).
• Free fluid in the pouch of Douglas (echogenic = blood).

5. Adjuncts

• Serum progesterone: < 5 ng/mL suggests a non-viable pregnancy; > 20 ng/mL favours a healthy IUP.
• Culdocentesis (historical): aspiration of non-clotting blood from the pouch of Douglas confirmed haemoperitoneum — now largely replaced by TVS.
• Laparoscopy: the gold standard, both diagnostic and therapeutic.

High-yield: TVS is the single best non-invasive investigation; diagnostic laparoscopy is the overall gold standard. The most specific sonographic sign is the tubal ring / bagel sign.

Management

Choice depends on haemodynamic stability, β-hCG level, sac size, fetal cardiac activity, and the patient's desire for future fertility. The three options are expectant, medical (methotrexate), and surgical.

A. Expectant management

For a clinically stable, asymptomatic woman with a small, declining β-hCG (e.g., < 1000–1500 mIU/mL and falling) and no fetal cardiac activity. Requires reliable follow-up with serial β-hCG.

B. Medical management — Methotrexate (MTX)

MTX is a folate antagonist that inhibits dihydrofolate reductase, halting rapidly dividing trophoblast.

Best candidates / inclusion criteria:

• Haemodynamically stable, no signs of rupture.
• β-hCG < 5000 mIU/mL (best results < 1500–2000).
• Ectopic mass < 3.5–4 cm.
• No fetal cardiac activity.
• No significant free fluid / haemoperitoneum.
• Reliable for follow-up; normal baseline LFT, renal function, and blood counts.

Absolute contraindications: haemodynamic instability/rupture, breastfeeding, immunodeficiency, hepatic/renal/haematological disease, peptic ulcer, active pulmonary disease, coexistent viable IUP (heterotopic), hypersensitivity to MTX.

Single-dose regimen: MTX 50 mg/m² IM on day 1. Measure β-hCG on day 4 and day 7; expect a ≥ 15% fall between days 4 and 7. If the fall is inadequate, give a second dose (up to 4 doses). Follow weekly until undetectable.

High-yield: A rise in β-hCG between day 1 and day 4 is normal/expected after MTX. Success is judged by a ≥ 15% drop from day 4 to day 7. Advise the patient to avoid folic acid, NSAIDs, alcohol, and intercourse and to use reliable contraception for ~3 months afterwards.

C. Surgical management

Indicated when the patient is haemodynamically unstable, has signs of rupture, has a large mass / high β-hCG, fetal cardiac activity, or fails/contraindicates MTX.

Two operations on the tube:

	Salpingostomy (linear, conservative)	Salpingectomy (removal of tube)
What	Linear incision on antimesenteric tube, evacuate ectopic, leave tube	Remove the affected tube entirely
Preferred when	Contralateral tube damaged/absent; fertility-sparing desired	Contralateral tube healthy; ruptured/severely damaged tube; uncontrolled bleeding; recurrent ectopic in same tube
Pros	Preserves tube for future fertility	Definitive; lower persistent trophoblast risk
Cons	Risk of persistent trophoblast (~5–20%) → follow β-hCG; higher recurrence in that tube	Loss of tube

High-yield (the most-tested decision): Choose salpingostomy when you want to save the tube — especially if the other tube is diseased or absent. Choose salpingectomy when the contralateral tube is healthy, the tube is ruptured/badly damaged, or bleeding is uncontrolled. After salpingostomy, monitor serial β-hCG for persistent trophoblastic tissue.

Route: Laparoscopy is preferred in the stable patient (less blood loss, faster recovery). Laparotomy is reserved for the unstable/shocked patient or massive haemoperitoneum.

D. Anti-D and resuscitation

• Give anti-D immunoglobulin to all Rh-negative women managed surgically (and per local policy for medical management).
• In a ruptured ectopic with shock: resuscitate first — wide-bore IV access, crystalloids/blood, cross-match — and proceed to emergency laparotomy/laparoscopy without delay. Do not wait for confirmatory imaging in a collapsing patient.

Complications

• Tubal rupture → massive intraperitoneal haemorrhage → hypovolaemic shock and death (leading cause of first-trimester maternal mortality).
• Recurrent ectopic (~10–15% after one ectopic).
• Infertility / subfertility from tubal damage.
• Persistent trophoblast after conservative surgery — rising/plateauing β-hCG; treat with MTX.
• Chronic ectopic — slow leak forming a pelvic haematocele/mass.
• Rh sensitisation if anti-D omitted.

Key Differentials

Condition	Distinguishing clue
Threatened/incomplete miscarriage	β-hCG falling; IUP/products in uterus on TVS
Ruptured corpus luteum / haemorrhagic ovarian cyst	Negative UPT; cyst on ovary
Acute PID / tubo-ovarian abscess	Fever, discharge, bilateral tenderness; UPT usually negative
Acute appendicitis	RLQ pain, fever, leucocytosis; UPT negative
Ovarian torsion	Sudden severe pain, vomiting; whirlpool sign on Doppler
Pregnancy of unknown location	Positive UPT, no sac anywhere yet — follow β-hCG

High-yield: The pivotal first step separating gynaecological emergencies is the urine pregnancy test. A positive test with pain/bleeding and an empty uterus on TVS = ectopic until proven otherwise.

Eponyms, Signs & Mnemonics

• Spalding's triad — amenorrhoea + irregular bleeding + lower abdominal pain (ectopic). (Spalding's sign = overlapping fetal skull bones = IUD — don't mix these up.)
• Cullen's sign — periumbilical bruising (also seen in acute pancreatitis).
• Arias-Stella reaction — atypical hypersecretory endometrial change seen histologically with ectopic (and other gestations); not pathognomonic.
• Spiegelberg criteria — for diagnosing ovarian ectopic.
• Mnemonic for MTX eligibility — "Stable, Small, Slow, Silent": Stable haemodynamics, Small mass (< 3.5 cm), Slow/low β-hCG (< 5000), Silent heart (no fetal cardiac activity).

Recently asked / exam angle

• β-hCG discriminatory zone numbers: "At what β-hCG should an intrauterine sac be visible on TVS?" → 1500–2000 mIU/mL.
• MTX day-4 to day-7 rule: expect ≥ 15% fall; a rise from day 1→4 is normal.
• Salpingostomy vs salpingectomy vignettes: decision hinges on the status of the contralateral tube and haemodynamic stability — the single most repeated MCQ stem.
• Commonest site = ampulla; earliest rupture = isthmus; latest but most dangerous rupture = interstitial/cornual.
• Strongest risk factor = previous ectopic pregnancy.
• Heterotopic pregnancy association with IVF/ART and the trap of a reassuring intrauterine sac.
• Spalding's triad vs Spalding's sign distinction.
• Anti-D in Rh-negative women — frequently the "best next step" distractor.
• Image-based: tubal ring / bagel sign and pseudo-gestational sac.

Rapid revision

1. Ectopic = implantation outside the endometrial cavity; ~1–2% of pregnancies; commonest cause of first-trimester maternal death.
2. Ampulla = commonest site; isthmus ruptures earliest; interstitial/cornual ruptures latest but bleeds most.
3. Previous ectopic is the strongest risk factor; PID, tubal surgery, IUCD-with-pregnancy, IVF, smoking also raise risk.
4. Spalding's triad = amenorrhoea + irregular bleeding + lower abdominal pain; shoulder-tip pain = haemoperitoneum.
5. Discriminatory zone = 1500–2000 mIU/mL on TVS — no intrauterine sac above this = ectopic.
6. Normal IUP β-hCG rises ≥ 53–66% / 48 h; suboptimal rise suggests ectopic.
7. Most specific TVS sign = tubal ring / bagel sign; beware the pseudo-gestational sac.
8. Laparoscopy = diagnostic and therapeutic gold standard; culdocentesis (non-clotting blood) is historical.
9. MTX criteria: stable, β-hCG < 5000, mass < 3.5 cm, no fetal cardiac activity, no rupture; success = ≥ 15% fall day 4→7.
10. Salpingostomy if the other tube is damaged (save fertility) → watch for persistent trophoblast; salpingectomy if other tube is healthy or tube is ruptured/bleeding.
11. Unstable patient → resuscitate + emergency surgery (laparotomy); never delay for imaging.
12. Give anti-D to Rh-negative women; recurrence risk after one ectopic is ~10–15%.