Describe the sites, risk factors, clinical features, diagnosis and management of ectopic Pregnancy.

Definition

An ectopic pregnancy is the implantation of the fertilised ovum outside the normal uterine (endometrial) cavity. It is a leading cause of maternal death in early pregnancy and a true gynaecological emergency when it ruptures.

Ectopic Pregnancy - Management Options

Sites

Tubal pregnancy (≈ 95%) is commonest — most often in the ampulla, then the isthmus, fimbria and (dangerously) the interstitial/cornual part. Rarer sites are ovarian, cervical, caesarean-scar and abdominal pregnancies.

Risk Factors

Anything damaging the tube or delaying ovum transport — pelvic inflammatory disease/salpingitis, previous tubal surgery or previous ectopic, endometriosis, IUCD in situ, assisted reproduction, tubal-ligation failure and smoking.

Fate of a Tubal Pregnancy

The thin-walled tube cannot sustain the pregnancy, which usually ends in one of three ways: tubal abortion (extrusion of the conceptus into the peritoneal cavity, commonest in ampullary pregnancy), tubal rupture (into the peritoneal cavity with severe intraperitoneal haemorrhage, commonest in the narrow isthmus) or, rarely, spontaneous tubal mole/absorption.

Clinical Features

The classic triad is amenorrhoea, lower-abdominal pain and abnormal vaginal bleeding (slight, dark). Rupture produces an acute abdomen — severe pain, signs of haemorrhagic shock, shoulder-tip pain (diaphragmatic irritation), abdominal distension, and on examination marked tenderness, cervical excitation/motion tenderness and a tender adnexal fullness.

Investigations

• Urine and serum β-hCG — a sub-optimal rise (failure to double in 48 h) suggests an abnormal pregnancy.
• Transvaginal ultrasound — an empty uterus with an adnexal mass (± gestational sac/cardiac activity) and free fluid in the pouch of Douglas; correlated with the hCG "discriminatory zone".
• Laparoscopy — the gold standard for diagnosis (and treatment); culdocentesis showing non-clotting blood in resource-limited settings.

Differential Diagnosis

Threatened or incomplete miscarriage, a ruptured or haemorrhagic ovarian cyst, acute pelvic inflammatory disease/salpingitis, torsion of an ovarian mass, and acute appendicitis.

Management

• Expectant — for a small, stable, asymptomatic ectopic with low and falling β-hCG.
• Medical — methotrexate (single-dose, with hCG follow-up) in the stable patient meeting criteria: hCG < 5000 IU/L, mass < 3.5 cm, no fetal cardiac activity and no rupture.
• Surgical — laparoscopic salpingectomy (or salpingostomy if the other tube is damaged) for the stable patient; laparotomy for the ruptured/haemodynamically unstable patient after resuscitation.
• Give anti-D to Rh-negative women.

An ectopic pregnancy implants outside the uterine cavity — in 98% of cases in the fallopian tube, and most often in the ampulla. Because the tube cannot expand, the invading trophoblast erodes through its wall into the rich vessels of the mesosalpinx, causing catastrophic intraperitoneal haemorrhage. The classic triad is amenorrhoea, abdominal pain and irregular vaginal bleeding; diagnosis rests on β-hCG with transvaginal ultrasound — an empty uterus with β-hCG above the discriminatory zone means an ectopic until proved otherwise.

WHY Ectopic Pregnancy Is an Emergency — the Tube Cannot Expand

Understanding why an ectopic pregnancy ruptures, and why it kills, explains its status as the classic gynaecological emergency. A pregnancy implanted in the tube behaves exactly as one implanted in the uterus: the trophoblast invades the wall aggressively, eroding blood vessels in order to establish a blood supply. But the fallopian tube is a thin, muscular, non-distensible structure — it has none of the uterus's capacity to hypertrophy and expand. So as the pregnancy grows, it erodes through the tubal wall, tearing into the rich vessels of the mesosalpinx and broad ligament — and because these bleed into the free peritoneal cavity, the haemorrhage is unconfined and can be catastrophic. The woman may collapse with hypovolaemic shock, shoulder-tip pain (blood irritating the diaphragm) and abdominal distension — while her external vaginal bleeding is only slight, so the visible loss badly underestimates the true one. This is why a woman of reproductive age with abdominal pain and collapse must have a pregnancy test, and why rupture demands immediate resuscitation and laparotomy — not investigation. It also explains why an isthmic ectopic (in the narrow, thick-walled segment) ruptures earliest, while an ampullary one (the commonest site) may present later.

WHY Early Diagnosis Transformed the Treatment

A useful concept is why ectopic pregnancy, once an operation, is now often a medical or even conservative diagnosis — the entire change resting on earlier diagnosis. Formerly the diagnosis was made only at rupture, so the treatment was necessarily emergency salpingectomy. Today, the combination of a sensitive serum β-hCG and high-resolution transvaginal ultrasound allows detection before rupture: the key principle is that once the β-hCG rises above the 'discriminatory zone' (about 1500–2000 IU/L), an intrauterine gestation sac should be visible — so an empty uterus at that level means an ectopic until proved otherwise; and a suboptimal rise in serial β-hCG (failing to increase by ~66% in 48 hours) suggests a non-viable or ectopic pregnancy. This early diagnosis opens gentler options: medical treatment with methotrexate (for a small, unruptured ectopic with a low β-hCG, no cardiac activity and a stable patient) avoids surgery altogether; and, when surgery is needed, a laparoscopic salpingostomy may conserve the tube. Understanding that early diagnosis, not new drugs, is what made conservative treatment possible explains the modern emphasis on early pregnancy assessment.

• Ectopic pregnancy: implantation outside the uterine cavity — 98% tubal, the ampulla commonest (~70%); the isthmus ruptures earliest.
• Risk factors: previous PID/salpingitis, tubal surgery, previous ectopic, IUCD in situ, IVF, smoking, endometriosis.
• Classic triad: amenorrhoea + abdominal pain + irregular vaginal bleeding; rupture → shock, shoulder-tip pain, cervical excitation — visible bleeding underestimates the loss.
• Diagnosis: β-hCG + transvaginal ultrasound — an empty uterus with β-hCG above the discriminatory zone (~1500–2000 IU/L) means ectopic until proved otherwise.
• Treatment: ruptured → resuscitate and operate immediately (salpingectomy); unruptured, small, stable, low β-hCG → methotrexate or laparoscopic salpingostomy.