Definition of Missed Abortion
Missed abortion, also termed "silent miscarriage," is defined as embryonic or fetal death without spontaneous expulsion of conception products from the uterus, corresponding to the modern terminology "diagnostic of early pregnancy loss (EPL)" or "embryonic/fetal demise." 1, 2
Modern Terminology and Classification
The term "missed abortion" remains clinically acceptable, though contemporary guidelines recommend more precise terminology:
- Preferred modern terms: "Diagnostic of Early Pregnancy Loss (EPL)" or "Embryonic/Fetal Demise" are now recommended by ultrasound consensus guidelines 3, 1, 2
- Obsolete terms to avoid: "Blighted ovum," "pregnancy failure," and "nonviable pregnancy" should no longer be used 1, 2
- Gestational age distinction: The term "fetal demise" is specifically used when gestational age is ≥11 weeks 2
Diagnostic Ultrasound Criteria
The diagnosis is established by transvaginal ultrasound using specific measurements that confirm embryonic/fetal death with retained products:
- Crown-rump length (CRL) ≥7 mm without cardiac activity 1, 2, 4
- Mean sac diameter (MSD) ≥25 mm without visible embryo (anembryonic pregnancy) 1, 2, 4
- Absence of embryo ≥14 days after initial visualization of gestational sac 1, 2
Clinical Characteristics
The classic textbook definition (fetal death retained for ≥8 weeks) is rarely fulfilled in modern practice due to early ultrasound detection. 5 Key clinical features include:
- Vaginal spotting or bleeding occurs in approximately 92% of cases before diagnosis is established 6
- Average retention period: Typically 2.8 weeks from estimated time of demise to diagnosis, with retention exceeding 8 weeks occurring in only rare cases 6
- Often asymptomatic: Many patients have no symptoms, hence the term "silent miscarriage" 1
- Timing discrepancy: The onset of vaginal bleeding does not reflect the actual moment of embryonic/fetal death 6
Critical Management Implications
Expectant management is absolutely contraindicated in missed abortion due to significant maternal risks. 2 Active evacuation is required because:
- Infection risk: Intrauterine infection occurs in 38% of expectant management cases versus 13% with active treatment 2
- Hemorrhage risk: Postpartum hemorrhage occurs in 23.1% with expectant management versus 11% with active treatment 2
- Coagulopathy risk: Prolonged retention increases risk of disseminated intravascular coagulation 2
- Overall maternal morbidity: 60.2% with expectant management versus 33% with abortion care 2
Common Pitfalls to Avoid
- Do not wait for fever to diagnose infection; look for maternal tachycardia, purulent cervical discharge, and uterine tenderness as early signs 2
- Do not delay treatment waiting for spontaneous expulsion, as risks increase with time 2
- Do not confuse with ectopic pregnancy: Presence of intrauterine gestational sac rules out ectopic pregnancy 2
- Do not forget Rh immunoprophylaxis: All Rh-negative women require 50 μg anti-D immunoglobulin 2