Ectopic pregnancy Study Guide

📖 Core Concepts Ectopic pregnancy: implantation of a fertilized egg outside the uterine cavity (extrauterine). Typical location: 90 % in the fallopian tube (ampulla ≈80 % of tubal cases); others – cervix, ovary, abdominal cavity, cesarean‑section scar. Pregnancy of Unknown Location (PUL): positive pregnancy test + no gestational sac on transvaginal ultrasound. β‑hCG: hormone produced by trophoblast; its quantitative pattern helps differentiate viable intra‑uterine, failing, or ectopic pregnancies. Primary imaging: transvaginal ultrasonography (TVUS) – >90 % sensitivity for tubal ectopic gestation. Leading cause of first‑trimester maternal death (≈6–13 % of pregnancy‑related deaths). 📌 Must Remember Incidence: 1–2 % of all pregnancies (≈11–20/1 000 live births); ↑ to 4 % with assisted reproductive technology. β‑hCG “red flag”: >1500 mIU/mL without intra‑uterine sac on TVUS → high suspicion for ectopic. β‑hCG rise: <35 % increase in 48 h = abnormal (suggests ectopic or failing). Ultrasound signs: Blob sign – inhomogeneous adnexal mass, 84 % sensitivity, 99 % specificity. Bagel sign – empty extrauterine gestational sac, seen in 20 % of cases. Methotrexate criteria: β‑hCG low (generally <5000 mIU/mL), ectopic mass ≤3.5 cm, hemodynamically stable, no rupture, normal renal/hepatic function. Surgical indication: rupture, fetal cardiac activity, hemodynamic instability, or mass >3.5 cm with high β‑hCG. Future fertility (2‑year intra‑uterine pregnancy rates): Salpingectomy (radical) ≈ 64 % Methotrexate ≈ 67 % Conservative surgery (salpingostomy) ≈ 70 % 🔄 Key Processes Initial evaluation of suspected ectopic Obtain serum β‑hCG. Perform TVUS. If β‑hCG >1500 mIU/mL and no intra‑uterine sac → treat as probable ectopic. β‑hCG serial monitoring Draw β‑hCG every 48 h. Calculate percent change: $$\% \Delta = \frac{hCG{48h} - hCG{0h}}{hCG{0h}} \times 100$$ <35 % rise → abnormal → consider ectopic. Management decision algorithm Stable, low β‑hCG, small mass → expectant or methotrexate. Unstable, large mass, rupture, or high β‑hCG → surgical (laparoscopic preferred). Methotrexate protocol (single‑dose) Give 50 mg/m² IM. Re‑check β‑hCG on day 4 and day 7. If ≥15 % decline from day 4 to day 7 → continue; otherwise give second dose. Follow‑up of PUL Serial β‑hCG + repeat TVUS every 48–72 h until location is resolved or ectopic confirmed. 🔍 Key Comparisons Tubal site vs. non‑tubal ectopic Tubal (90 %): ampulla (≈80 %), fimbrial (≈5 %), isthmic (≈12 %), interstitial/cornual (≈2 %). Non‑tubal: cervix, ovary, abdomen, scar – much rarer, often present with atypical pain. Expectant vs. Medical vs. Surgical Expectant: low β‑hCG, no rupture, close monitoring; avoids drug/surgery but requires compliance. Methotrexate: medical, preserves tube, needs strict β‑hCG follow‑up; contraindicated in liver/renal dysfunction. Surgery: definitive, required for rupture or hemodynamic compromise; may sacrifice tube (salpingectomy) or preserve (salpingostomy). β‑hCG threshold vs. Ultrasound finding β‑hCG >1500 mIU/mL without intra‑uterine sac → high suspicion. TVUS directly visualizes extrauterine sac or “blob” sign; definitive when seen. ⚠️ Common Misunderstandings “All ectopics present with pain/bleeding.” Up to 10 % are asymptomatic; one‑third have no clinical signs. “β‑hCG >1500 mIU/mL always means ectopic.” Some early intra‑uterine pregnancies may still lack a visible sac; correlate clinically and repeat imaging. “Methotrexate harms future fertility.” Evidence shows no adverse effect on subsequent oocyte retrieval or overall fertility. “Salpingectomy always better than salpingostomy.” Tubal preservation (salpingostomy) yields slightly higher future intra‑uterine pregnancy rates; choice depends on rupture status and surgeon expertise. 🧠 Mental Models / Intuition “Rise‑Fall Curve”: Normal intra‑uterine pregnancy → β‑hCG roughly doubles every 48 h (≈100 % increase). Anything sub‑doubling (especially <35 % rise) flags ectopic/failing. “Location → Risk”: The farther the implantation from the uterus (e.g., abdominal), the higher the risk of catastrophic hemorrhage; always assume tubal rupture if hemodynamic instability. “Rule of 1500”: Treat any β‑hCG >1500 mIU/mL with a missing intra‑uterine sac as an urgent red flag—prompt action needed. 🚩 Exceptions & Edge Cases Very early intra‑uterine pregnancy may have β‑hCG <1500 mIU/mL and no sac → observation, repeat β‑hCG in 48 h. Persistent ectopic after conservative surgery: rising β‑hCG despite removal of visible mass → may need repeat methotrexate or secondary surgery. IUD users: higher proportion of pregnancies that do occur are ectopic; still low absolute risk but maintain high suspicion. Assisted reproduction: incidence 4 %; consider ectopic even with low β‑hCG if symptoms present. 📍 When to Use Which Expectant: β‑hCG <200 mIU/mL, mass <2 cm, no pain/bleeding, reliable follow‑up. Methotrexate: β‑hCG 200–5000 mIU/mL, mass ≤3.5 cm, stable vitals, normal liver/renal labs, no fetal heartbeat. Laparoscopic salpingostomy: stable patient, desire for future fertility, tube not severely damaged, mass ≤3.5 cm. Laparoscopic/ open salpingectomy: rupture, hemodynamic instability, large mass >3.5 cm, fetal cardiac activity, or severely damaged tube. 👀 Patterns to Recognize Shoulder pain + abdominal pain → intraperitoneal blood irritating diaphragm → suggests ruptured ectopic. “Blank” TVUS with β‑hCG >1500 → classic picture of ectopic or PUL needing close monitoring. Slow β‑hCG rise + “blob” on TVUS → high likelihood of tubal ectopic. Rapid β‑hCG rise (>100 % in 48 h) + intra‑uterine sac → normal early intra‑uterine pregnancy. 🗂️ Exam Traps Trap: “β‑hCG >1500 mIU/mL always confirms ectopic.” Why tempting: memorized “rule of 1500”. Why wrong: early intra‑uterine pregnancies may still lack a sac; repeat scan is needed. Trap: “Methotrexate is contraindicated in women who desire future pregnancy.” Why tempting: assumption that chemotherapy harms fertility. Why wrong: studies show no adverse effect on later fertility or oocyte retrieval. Trap: “All tubal ectopics are treated with salpingectomy.” Why tempting: salpingectomy is common in textbooks. Why wrong: salpingostomy is appropriate for stable patients desiring fertility preservation. Trap: “Presence of free fluid on TVUS automatically means rupture.” Why tempting: free fluid = bleeding. Why wrong: Small amounts can be physiologic or from minor leakage; assess hemodynamics and pain severity. --- Use this guide for a quick, high‑yield review before your exam. Focus on the “Rule of 1500”, the β‑hCG rise pattern, and the management algorithm – they appear on virtually every test question.