Diagnosis of Embryonic Demise Based on ISUOG and ACOG Guidelines
Embryonic demise is definitively diagnosed on transvaginal ultrasound when an embryo measures ≥7 mm crown-rump length (CRL) without cardiac activity, or when a gestational sac has a mean sac diameter (MSD) ≥25 mm without a visible embryo. 1, 2
Definitive Diagnostic Criteria for Embryonic/Fetal Demise
The following ultrasound findings are diagnostic of early pregnancy loss and require no repeat imaging:
Crown-rump length ≥7 mm without cardiac activity - This is the most commonly used criterion and confirms embryonic demise with 100% certainty 1, 2, 3
Mean sac diameter ≥25 mm without a visible embryo - This confirms anembryonic pregnancy (previously termed "blighted ovum," a term now considered obsolete) 1, 2
Absence of embryo with cardiac activity ≥14 days after initial visualization of a gestational sac without yolk sac - This time-based criterion is used when the initial scan showed only a gestational sac 1, 3
Absence of embryo with cardiac activity ≥11 days after initial visualization of a gestational sac with yolk sac - This shorter interval applies when a yolk sac was present on the initial scan 1, 3
Findings Suggestive But Not Diagnostic of Embryonic Demise
These findings raise concern but require follow-up ultrasound in 7-10 days before making a definitive diagnosis:
Embryo <7 mm CRL without cardiac activity - While concerning, measurement variability and the possibility of very early viable pregnancy mandate repeat imaging 1, 2
Mean sac diameter 16-24 mm without visible embryo - Requires follow-up as some normal pregnancies may have larger sacs before the embryo becomes visible 1, 3
Gestational sac >8 mm without yolk sac - Although a yolk sac is usually visible by this size, normal variation exists 1
Critical Pitfalls to Avoid
Never diagnose embryonic demise based on a single measurement if the CRL is <7 mm, even if cardiac activity is absent, as this can lead to inadvertent termination of a viable pregnancy 1, 2, 3. The threshold was increased from the historical 5 mm cutoff specifically to maximize diagnostic certainty and account for measurement variability 1.
Always use transvaginal ultrasound for first-trimester evaluation, not transabdominal ultrasound alone, as transvaginal imaging provides superior resolution and earlier detection of cardiac activity 1, 3.
Confirm gestational age by last menstrual period to avoid dating errors that could lead to misdiagnosis - a discrepancy between dates and ultrasound measurements may indicate either dating error or early demise 2, 3.
Document exact measurements with CRL measured along the longest axis of the embryo to ensure accuracy and reproducibility 3.
Additional Ultrasound Findings Associated with Nonviable Pregnancy
While not diagnostic alone, these findings increase concern for pregnancy loss:
Embryonic bradycardia (<100 beats/min before 6.3 weeks) - particularly when there is discordance between gestational age by biometrics versus last menstrual period 1, 4
Small gestational sac relative to embryo size 1
Enlarged or empty amniotic cavity 1
Abnormal yolk sac size or shape (normal yolk sac is 3-6 mm) 1
Terminology Recommendations
Use "embryonic demise" or "fetal demise" (the latter specifically at ≥11 weeks gestation) rather than outdated terms like "blighted ovum," "missed abortion," or "pregnancy failure" 2, 3, 5. The Society of Radiologists in Ultrasound recommends the umbrella term "Early Pregnancy Loss (EPL)" with specific subcategories 2, 3.
Management Implications After Diagnosis
Once embryonic demise is confirmed, expectant management is contraindicated due to increased risks of intrauterine infection (38% vs 13%), postpartum hemorrhage (23.1% vs 11%), and overall maternal morbidity (60.2% vs 33%) compared to active management 2, 5. Active evacuation via medical or surgical methods should be offered 2.
All Rh-negative women must receive 50 μg anti-D immunoglobulin to prevent alloimmunization, as fetomaternal hemorrhage occurs in approximately 32% of spontaneous abortions 2.