Illness script

Ectopic Pregnancy

Reproductive-age woman with amenorrhea, unilateral pelvic pain, and vaginal bleeding plus positive pregnancy test.

This illness script for Ectopic Pregnancy covers the classic presentation, who it affects, how you work it up, the mechanism, and first-line treatment—written for USMLE Step 1 and clerkship clinical reasoning.

Updated Jul 18, 2026All scripts

01

Who it affects

  • Reproductive-age women, most common in first trimester
  • Prior ectopic, PID/salpingitis, tubal surgery
  • IUD in place, prior tubal ligation
  • Assisted reproductive technology, smoking
  • History of chlamydia/gonorrhea, endometriosis

02

Diagnostics & workup

  • Positive urine/serum β-hCG with amenorrhea
  • Transvaginal US: no intrauterine gestational sac at discriminatory zone (β-hCG >1500-2000)
  • Adnexal mass or tubal ring; free fluid in cul-de-sac
  • Serial β-hCG: abnormal rise (<35-53% over 48h)
  • Ampulla of fallopian tube most common site
  • Rule out ruptured ectopic: peritonitis, hypotension, shoulder pain

03

Pathophysiology

  • Implantation of embryo outside uterine cavity, usually fallopian tube
  • Impaired tubal transport allows premature implantation
  • Trophoblast invades tubal wall causing distension and bleeding
  • Tubal rupture leads to hemoperitoneum and shock
  • Cannot support fetal viability

04

Treatment

  • Stable, small, low β-hCG, no fetal cardiac activity: IM methotrexate
  • Methotrexate contraindicated in hepatic/renal disease, rupture, cytopenias
  • Follow β-hCG after methotrexate to confirm decline
  • Unstable or ruptured: emergent surgery (laparoscopic salpingostomy/salpingectomy)
  • Give Rh(D) immune globulin if Rh-negative
  • Serial monitoring; counsel on future ectopic risk

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Educational use only. This illness script is a study framework, not medical advice. Confirm decisions with current guidelines and your clinical supervisors.