Early Pregnancy Failure (Loss) Criteria on Ultrasound: SRU 2024

TL;DR: The ultrasound thresholds that diagnose a first-trimester pregnancy loss have not changed since Doubilet et al. published them in the NEJM in 2013 — a crown-rump length (CRL) ≥7 mm with no cardiac activity, or a mean sac diameter (MSD) ≥25 mm with no embryo. What has changed is the language. The 2024 Society of Radiologists in Ultrasound (SRU) multisociety lexicon retired “pregnancy failure,” “heartbeat,” “viable,” “nonviable,” “blighted ovum,” and “pseudosac”. This page gives you the thresholds and the current terminology to report them in.

Findings Diagnostic of Early Pregnancy Loss

These findings are specific enough to act on. Each was selected to drive the false-positive rate to essentially zero, because the cost of an error is terminating a normal pregnancy.

• CRL ≥7 mm and no cardiac activity → report as embryonic demise.
• MSD ≥25 mm and no embryo → report as anembryonic pregnancy.
• Absence of an embryo with cardiac activity ≥2 weeks after a scan that showed a gestational sac without a yolk sac.
• Absence of an embryo with cardiac activity ≥11 days after a scan that showed a gestational sac with a yolk sac.
• No cardiac activity at a gestational age ≥11 weeks 0 days → report as fetal demise (the embryo becomes a fetus at 11w0d).

Findings Concerning For, But Not Diagnostic Of, Early Pregnancy Loss

These warrant follow-up transvaginal ultrasound, typically at 7–10 days — not intervention.

• CRL <7 mm and no cardiac activity
• MSD 16–24 mm and no embryo
• Absence of an embryo with cardiac activity 7–13 days after a scan showing a gestational sac without a yolk sac
• Absence of an embryo with cardiac activity 7–10 days after a scan showing a gestational sac with a yolk sac
• Absence of an embryo ≥6 weeks after the last menstrual period
• Expanded amnion sign (amnion visible adjacent to the yolk sac, with no visible embryo)
• Enlarged yolk sac (>7 mm)
• Small gestational sac relative to the embryo (<5 mm difference between MSD and CRL)
• Calcified yolk sac

The SRU-preferred way to convey this group is concerning for early pregnancy loss, or intrauterine pregnancy of uncertain prognosis. Both replace the old “pregnancy of uncertain viability.”

What Changed in 2024: The SRU First-Trimester Lexicon

The SRU convened a multisociety panel (radiology, obstetrics, emergency medicine, family planning, pediatrics) and reached ≥80% Delphi consensus on a shared first-trimester vocabulary. It was published simultaneously in Radiology and the American Journal of Obstetrics and Gynecology in August 2024. The thresholds above were left intact; the words used to report them were not.

Two motivations drove the changes. First, precision: “heartbeat” implies formed cardiac chambers that do not exist at 6 weeks. Second, patient impact — terms like “failure,” “incompetent,” and “abortion” are read by patients in their own portal reports, and the panel judged them needlessly harmful.

The panel also discourages calling the study a “viability scan.”

The Five Categories of Early Pregnancy Loss

Rather than a scatter of legacy nouns, the lexicon uses EPL as the root term with modifiers:

1. Concerning for EPL — findings that raise suspicion but do not meet threshold. Follow up.
2. Diagnostic of EPL — embryonic demise, fetal demise, or anembryonic pregnancy.
3. EPL in progress — the gestational sac is in the lower uterine segment or endocervical canal and moves with transducer pressure. The sliding sign distinguishes this from a cervical ectopic, which is implanted and will not slide.
4. Incomplete EPL — residual intrauterine tissue after partial passage. Retained products of conception (RPOC) remains an acceptable alternate term.
5. Completed EPL — the sac has passed and no residual tissue is seen.

Why the Thresholds Are Deliberately Conservative

The older cutoffs — CRL 5 mm, MSD 16 mm — were derived from small series and turned out to be unsafe. When they were tested against outcomes, pregnancies meeting them occasionally went on to deliver. The 2013 revision targeted a specificity of 100%, accepting delayed diagnosis as the lesser harm.

The largest prospective validation, a seven-centre UK study of 2,845 women (Preisler et al., BMJ 2015), confirmed the cutoffs hold: MSD ≥25 mm with an empty sac and CRL ≥7 mm without cardiac activity were both 100% specific. It also added two refinements worth knowing:

• Gestational age matters. After 70 days’ gestation, the thresholds can be tightened safely — MSD ≥18 mm without an embryo, or CRL ≥3 mm without cardiac activity, were each 100% specific in that cohort. The universal 7 mm / 25 mm cutoffs ignore this.
• The follow-up intervals are the weak link. The authors concluded the recommended re-scan timings are still too liberal. For a sac without an embryo and MSD <12 mm, failure of the diameter to double by ≥14 days was 100% specific; where MSD was ≥12 mm, absent cardiac activity at ≥7 days was 100% specific.

Practical consequence: when you are close to a threshold, the safe move is always the repeat scan. No single measurement in this range should trigger intervention.

Measurement Technique Pitfalls

• MSD is the average of three orthogonal inner-to-inner diameters — length, width, and depth of the fluid only. Including the echogenic rim inflates it toward the 25 mm threshold.
• CRL must be measured in a true midsagittal plane with the embryo neutral, excluding the yolk sac. An oblique plane underestimates; a flexed or hyperextended embryo does too.
• Use transvaginal, not transabdominal, imaging for these decisions. The thresholds were derived from transvaginal data.
• M-mode, not spectral Doppler, to document cardiac activity in the first trimester — keep the acoustic output down.
• Once an embryo is measurable, CRL supersedes MSD for dating. You can check your numbers against our gestational age calculator using CRL and MSD.

Definite IUP, Probable IUP, and Pregnancy of Unknown Location

The lexicon formalised a three-tier framework for locating the pregnancy:

• Definite IUP — an intrauterine gestational sac containing a yolk sac or embryo.
• Probable IUP — a rounded intrauterine collection with an intradecidual sign or double decidual sac sign, but no yolk sac or embryo yet.
• Pregnancy of unknown location (PUL) — positive hCG with neither a definite nor probable IUP nor an ectopic pregnancy visible transvaginally.

Note two specific traps. “Pseudosac” is retired — call it intracavitary fluid, because the term implied an ectopic that may not be there. And an eccentrically located sac completely surrounded by endometrium is an IUP; the panel discourages “angular” and “cornual pregnancy” for it.

hCG in a Pregnancy of Unknown Location

• A single hCG value does not distinguish ectopic from intrauterine pregnancy, viable or otherwise.
• If hCG is <3000 mIU/mL, presumptive methotrexate or surgical treatment for ectopic should not be undertaken — the risk of interrupting a normal intrauterine pregnancy is real.
• If hCG is ≥3000 mIU/mL with no sac seen, a normally progressing IUP is possible but unlikely; the most likely diagnosis is early pregnancy loss. Obtain at least one follow-up hCG and repeat ultrasound before treating for ectopic.
• hCG in ectopic pregnancy is highly variable and often <1000 mIU/mL, and the level does not predict rupture. If the clinical picture is suspicious, scan regardless of the number.

Formal risk stratification has matured since 2013. In a two-centre Danish cohort of 773 women with PUL, the M6NP model (hCG-based, no progesterone) reached 97% sensitivity for ectopic pregnancy at 46% specificity, while the NICE criteria gave 91% sensitivity at 66% specificity. The initial scan itself stratifies well: a probable ectopic carried a 24% risk of ectopic, a probable IUP only 2.7%. Ectopic pregnancy complicates 5–20% of PUL, so your report’s location call materially changes the follow-up pathway.

Cesarean Scar Implantation Is an Ectopic Pregnancy

This is the single most clinically consequential reclassification in the lexicon. A pregnancy implanted in a cesarean section scar is now categorised as an ectopic pregnancy — the term is cesarean scar ectopic pregnancy, not “cesarean scar pregnancy” — because the implantation carries a high risk of uterine rupture, massive haemorrhage, and hysterectomy. The lexicon’s definition of ectopic is implantation in an abnormal location, whether extrauterine or intrauterine, which brings cervical, interstitial, intramural, and cesarean scar implantations under one heading.

Look for a gestational sac in the lower uterine segment at the scar, anterior myometrial thinning over the sac, and prominent peripheral vascularity. The absent sliding sign separates it from an EPL in progress passing through.

How to Word the Report

Lexicon-compliant impressions for the common scenarios:

• Intrauterine gestational sac with an embryo, CRL 9 mm, no cardiac activity. Findings are diagnostic of early pregnancy loss (embryonic demise).
• Intrauterine gestational sac, MSD 27 mm, no embryo. Diagnostic of early pregnancy loss (anembryonic pregnancy).
• Intrauterine gestational sac with an embryo, CRL 4 mm, no cardiac activity. Concerning for early pregnancy loss; intrauterine pregnancy of uncertain prognosis. Recommend follow-up transvaginal ultrasound in 7–10 days.
• No definite or probable intrauterine or ectopic pregnancy identified. Pregnancy of unknown location. Correlate with serial serum hCG.

Give the actual measurement alongside the conclusion. The referring clinician needs to see that you were above threshold, not just that you said so — and if the case is later reviewed, the number is the defence.

For scanning technique and the normal first-trimester milestones behind these criteria, see our early pregnancy ultrasound guide.

References

• Rodgers SK, Horrow MM, Doubilet PM, et al. A Lexicon for First-Trimester US: Society of Radiologists in Ultrasound Consensus Conference Recommendations. Radiology. 2024;312(2):e240122. PMID: 39189906. doi:10.1148/radiol.240122 (simultaneously published in Am J Obstet Gynecol. 2025;232(1):1-16; PMID: 39198135)
• Doubilet PM, Benson CB, Bourne T, et al. Diagnostic criteria for nonviable pregnancy early in the first trimester. N Engl J Med. 2013;369(15):1443-1451. PMID: 24106937. doi:10.1056/NEJMra1302417
• Preisler J, Kopeika J, Ismail L, et al. Defining safe criteria to diagnose miscarriage: prospective observational multicentre study. BMJ. 2015;351:h4579. PMID: 26400869. doi:10.1136/bmj.h4579
• Reza C, Hammerum MS, Michaud SJ, et al. Evaluating the performance of the M6 model without initial serum progesterone (M6NP) and the NICE guidelines in a Danish pregnancy of unknown location (PUL) population. Eur J Obstet Gynecol Reprod Biol. 2025;312:114526. PMID: 40517510. doi:10.1016/j.ejogrb.2025.114526
• Nippita S, Cansino C, Goldberg AB, et al. Society of Family Planning Clinical Recommendation: Management of undesired pregnancy of unknown location and abortion at less than 42 days of gestation. Contraception. 2025;150:110865. PMID: 40122324. doi:10.1016/j.contraception.2025.110865

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