Definition

Ectopic pregnancy is a condition where a fertilized egg implants outside the endometrium of the uterine cavity and poses significant risks if undiagnosed or mismanaged.

Epidemiology

Incidence is challenging to estimate due to decreased hospitalizations, increased healthcare visits, and difficulties in accurately counting early pregnancy failures not resulting in delivery or hospitalization. It is thought to affect up to 2% of pregnancies.

Mortality

Ectopic pregnancy is a significant cause of maternal morbidity and mortality. Haemorrhage from ectopic pregnancy is the leading cause of first-trimester maternal death, responsible for 4 to 10 percent of all pregnancy-related fatalities.

Risk factors

Ectopic pregnancy is primarily caused by disruptions in normal tubal anatomy, resulting from factors like infections, surgery, congenital abnormalities, or tumours. These anatomical changes often impair tubal function, including damaged ciliary activity. The highest risk is linked to a history of previous ectopic pregnancies or tubal surgery. Other risk factors for ectopic pregnancy include pelvic inflammatory disease, smoking, in vitro fertilization, intrauterine contraceptive devices and endometriosis.

Anatomic sites

Ectopic pregnancies typically implant in the fallopian tube (96%), with most occurring in the ampulla (70%), followed by the isthmus (12%) and fimbria (11%). Tubal pregnancies often result from conditions that hinder the movement of the fertilized egg into the uterus or factors causing premature implantation. Chronic salpingitis, found in up to 90% of tubal pregnancies, is a key contributor. Interstitial pregnancies, which occur in the proximal fallopian tube near the uterus, are rare and can be misdiagnosed as intrauterine due to partial implantation in the endometrium. Ectopic pregnancies also occur in the cervix, ovary, hysterectomy scar and abdomen, as well as in combination with an intrauterine pregnancy (heterotopic pregnancy).

Clinical manifestations

Ectopic pregnancy typically presents with abdominal pain and/or vaginal bleeding. It should be suspected in reproductive-aged patients with these symptoms, particularly those with risk factors. However, over 50% of patients remain asymptomatic before tubal rupture and may not exhibit identifiable risk factors. Patients with ectopic pregnancy can become hemodynamically unstable if the implantation site, typically the fallopian tube, ruptures and causes bleeding. Rupture should be suspected in those experiencing sudden, severe abdominal pain, faintness, or signs of hemodynamic instability (e.g., hypotension, tachycardia).

Diagnosis

For hemodynamically stable patients with a suspected ectopic pregnancy, a complete history and physical examination are conducted, along with serum beta-hCG measurement and US. At serum beta-hCG levels below 2000 IU, a normal early pregnancy may not be visible on US. Beta-hCG levels tend to rise more slowly in ectopic pregnancy. While a typical doubling rate in early pregnancy is about 48 hours, an increase of 50% or less over 48 hours strongly suggests a non-viable pregnancy, whether intrauterine or ectopic. While US provides crucial initial insights and remains the first-line imaging modality for symptomatic women in early pregnancy who present to the emergency department, CT is particularly valuable in complex cases or when the diagnosis remains uncertain.