Implantation outside the uterine cavity — most commonly tubal; life-threatening hemorrhage if ruptured.
Also known as: ectopic pregnancy, tubal pregnancy, ruptured ectopic, heterotopic pregnancy
Overview
Implantation of a fertilized ovum outside the uterine cavity; ~95% occur in the fallopian tube (ampulla most common). Non-tubal sites include cornual/interstitial, cervical, ovarian, abdominal, and cesarean scar pregnancies.
Epidemiology
~1-2% of all pregnancies in the US. Leading cause of maternal mortality in the first trimester (~4% of pregnancy-related deaths). Higher incidence with ART and PID.
Try two board-style Ectopic Pregnancy questions
Real questions from the FirstPassPA bank, with the full explanation. Pick an answer — no signup, no email.
Question 1ReproductiveMedium
A 16-year-old girl presents with severe lower abdominal pain and vaginal bleeding. Last menstrual period was 7 weeks ago. β-human chorionic gonadotropin (β-hCG) is 4,200 mIU/mL. Transvaginal ultrasound shows no intrauterine pregnancy and free pelvic fluid. BP is 82/54 mmHg and HR is 128/min. Which of the following is the most appropriate immediate management?
ABlood transfusion with inpatient observation
BEmergent surgical exploration
CDiagnostic laparoscopy after stabilization
DSingle-dose intramuscular methotrexate
Reveal answer & full explanation
Correct answer: B — Emergent surgical exploration
ABlood transfusion with inpatient observation
BEmergent surgical exploration✓
CDiagnostic laparoscopy after stabilization
DSingle-dose intramuscular methotrexate
Why emergent surgical exploration is correct
This is a ruptured ectopic pregnancy with hemodynamic instability (BP 82/54 mmHg, HR 128/min), which is a surgical emergency.
Free pelvic fluid on ultrasound indicates hemoperitoneum from rupture.
No intrauterine pregnancy on transvaginal ultrasound (TVUS) with β-human chorionic gonadotropin (β-hCG) of 4,200 mIU/mL — above the discriminatory zone of 1,500–2,500 mIU/mL — raises high suspicion for ectopic pregnancy.
Management: immediate IV access, type and crossmatch, fluid resuscitation, and emergent operating room for salpingectomy.
Why the others are wrong
A) Blood transfusion with inpatient observation — Transfusion supports the circulation but provides no source control; hemorrhage from the ruptured tube continues until it is operatively removed, so resuscitation must accompany surgery rather than substitute for it.
C) Diagnostic laparoscopy after stabilization — Diagnostic laparoscopy is the appropriate surgical approach when stable; however, with frank hemodynamic instability and suspected rupture, emergent exploration (which may require laparotomy) takes priority over a staged approach.
D) Single-dose intramuscular methotrexate — Contraindicated in this setting; methotrexate requires hemodynamic stability and no active bleeding.
Question 2ReproductiveMedium
A 26-year-old woman presents with sudden unilateral pelvic pain, vaginal spotting, and 7 weeks of amenorrhea. Beta-hCG is 2,800 mIU/mL. Transvaginal ultrasound shows no intrauterine pregnancy. She is hemodynamically stable. What is the management?
ARepeat beta-hCG in 48 hours
BDilation and curettage
CVaginal misoprostol
DMethotrexate 50 mg/m2 IM
Reveal answer & full explanation
Correct answer: D — Methotrexate 50 mg/m2 IM
ARepeat beta-hCG in 48 hours
BDilation and curettage
CVaginal misoprostol
DMethotrexate 50 mg/m2 IM✓
Why Methotrexate 50 mg/m2 IM is correct
Ectopic pregnancy is diagnosed when hCG is above the discriminatory zone (1,500-2,000 mIU/mL) with no intrauterine pregnancy (IUP) on transvaginal ultrasound (TVUS); hCG here is 2,800 mIU/mL
Methotrexate is appropriate when criteria are met: hemodynamic stability, no rupture, hCG below 5,000 mIU/mL, ectopic mass below 3.5 cm, no fetal cardiac activity, and normal renal/hepatic/CBC labs; this patient is stable with an hCG of 2,800, and the remaining criteria are confirmed before dosing
Why the others are wrong
Repeat beta-hCG in 48 hours — waiting with hCG above the discriminatory zone and no IUP on TVUS risks rupture
Dilation and curettage — does not treat a tubal ectopic pregnancy
Vaginal misoprostol — a uterotonic that expels an intrauterine gestation; it has no effect on trophoblast implanted in the tube and leaves the ectopic in place to rupture
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Prior tubal surgery (sterilization, reanastomosis)
Tubal pathology (PID, salpingitis, hydrosalpinx)
Pregnancy with IUD in place
Assisted reproductive technology
Endometriosis
Smoking
Diethylstilbestrol exposure (historical)
Infertility, advanced maternal age
Pathophysiology
Damaged or dysfunctional fallopian tubes impair ovum transport, leading to implantation in tubal mucosa. As trophoblast invades the thin tubal wall, hemorrhage occurs, leading to tubal distension, abortion, or rupture with intraperitoneal hemorrhage. β-hCG production is typically lower than in intrauterine pregnancy and rises more slowly.
Clinical presentation
Symptoms
Amenorrhea (missed period)
Unilateral pelvic or abdominal pain
Vaginal bleeding (often light)
Shoulder tip pain (referred from diaphragmatic blood)
Dizziness, syncope (hemorrhage)
Some are asymptomatic and detected on early pregnancy ultrasound
Heterotopic pregnancy — Concurrent intrauterine and ectopic — rare except with ART (~1:100 vs 1:30,000 spontaneous)
Diagnostic workup
Diagnostic criteria
Pregnancy of unknown location: positive β-hCG without IUP or extrauterine findings on TVUS — requires serial β-hCG and possibly D&C to distinguish failed IUP from ectopic. Ectopic confirmed by visualization of extrauterine pregnancy or by absence of chorionic villi on D&C with persistent or rising β-hCG.
Labs
Quantitative serum β-hCG — discriminatory zone ~1500-3500 mIU/mL above which intrauterine pregnancy should be visible on TVUS
Serial β-hCG every 48 hours: normal IUP doubles in 48 h (rises ≥35%); abnormal rise/plateau/fall suggests nonviable IUP or ectopic
CBC (anemia from bleeding), type and screen, Rh status
Quantitative β-hCG after definitive treatment to confirm resolution (<5 mIU/mL)
Imaging
Transvaginal ultrasound — primary imaging; look for intrauterine gestational sac (with yolk sac or embryo), adnexal mass, free fluid in pelvis
Doppler may show 'ring of fire' (vascular ectopic)
Definitive: extrauterine gestational sac with yolk sac/embryo or extrauterine cardiac activity
Pseudogestational sac (collapsed fluid in endometrial cavity) can mimic IUP — careful evaluation
Diagnostic algorithm
flowchart TD
A[Positive β-hCG +<br/>pain/bleeding] --> B[Hemodynamic status]
B -->|Unstable / rupture| C[Emergent laparoscopic<br/>salpingectomy<br/>blood products]
B -->|Stable| D[TVUS + quantitative β-hCG]
D --> E{IUP visible?}
E -->|Yes| F[Intrauterine pregnancy<br/>± heterotopic if ART/risk]
E -->|Ectopic seen| G[Treat ectopic]
E -->|Indeterminate| H{β-hCG vs<br/>discriminatory zone}
H -->|Above + no IUP| I[Likely ectopic or<br/>nonviable IUP — repeat US,<br/>± D&C, treat as ectopic if confirmed]
H -->|Below| J[Repeat β-hCG in 48 h]
J --> K{Rise ≥35%?}
K -->|Yes| L[Likely IUP — repeat US<br/>when above zone]
K -->|No| M[Nonviable: ectopic or<br/>failed IUP — definitive workup]
G --> N{MTX candidate?}
N -->|Yes| O[Methotrexate IM<br/>+ serial β-hCG]
N -->|No| P[Laparoscopic surgery]
Algorithm for suspected ectopic pregnancy.
Treatment
First-line
Hemodynamically unstable, ruptured, or large ectopic: emergent surgery (laparoscopic salpingectomy preferred over salpingostomy)
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