Early Pregnancy Viability Assessment (SRU 2013)

Step-by-step decision

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1. [Decision] Transvaginal ultrasound findings (SRU 2013)
   Transvaginal ultrasound findings (SRU 2013 criteria)? (Transvaginal measurement required. The discriminatory zone beta-hCG ~1500–2000 (more conservatively 3500) should show an intrauterine sac in a normal pregnancy; a single beta-hCG cannot distinguish viable/non-viable intrauterine from ectopic. Any round/oval intrauterine fluid collection + positive pregnancy test is usually a true gestational sac (do not mistake for a pseudosac).)
   • Embryonic cardiac activity seen (viable) → Viable intrauterine pregnancy
   • CRL ≥7 mm without heartbeat; or MSD ≥25 mm without embryo; or no heartbeat embryo ≥14 days after an empty sac/≥11 days after a sac with yolk sac → Diagnostic of early pregnancy loss
   • Equivocal, not diagnostic (CRL <7 mm without heartbeat, MSD 16–24 mm without embryo, empty amnion sign, yolk sac >7 mm, etc.) → Equivocal · follow up, do not intervene
   • Empty cavity, positive beta-hCG (PUL) → PUL → exclude ectopic
2. [End] Viable intrauterine pregnancy
   Embryonic cardiac activity seen = viable intrauterine pregnancy; follow up by gestation; if bleeding/pain, assess for threatened miscarriage/subchorionic hematoma.
3. [End] Diagnostic of early pregnancy loss
   Diagnostic of early pregnancy loss (100% specificity): CRL ≥7 mm without heartbeat / MSD ≥25 mm without embryo / empty sac ≥14 days / sac with yolk sac ≥11 days still without a heartbeat embryo → after clinical confirmation, expectant or medical (misoprostol) or surgical evacuation; give anti-D immunoglobulin if Rh-negative.
4. [End] Equivocal · follow up, do not intervene
   Equivocal, not at the diagnostic threshold: do not intervene, repeat at SRU intervals (7–13 days after an empty sac / 7–10 days after a sac with a yolk sac; repeat for CRL <7 mm without heartbeat); integrate with the beta-hCG trend.
5. [End] PUL → exclude ectopic
   Pregnancy of unknown location (PUL): empty cavity + positive beta-hCG, no definite intra- or extrauterine pregnancy → must exclude ectopic pregnancy; serial beta-hCG (48 h) + transvaginal ultrasound follow-up to diagnosis; abnormal beta-hCG rise/plateau or adnexal signs → suspect ectopic, manage as ectopic; hemodynamically unstable → emergency.

Source guidelines & references

• Early pregnancy non-viability diagnostic criteria (SRU consensus; NEJM 2013 Doubilet)
• First-trimester US lexicon (Radiology 2024)

This pathway is our own synthesis of the decision logic in the guidelines above (not the guideline verbatim); thresholds and workflows change as guidelines update — in practice follow the latest guideline, your institution's protocol and the individual patient.

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