What is an anembryonic cyst, also known as a blighted ovum?

Anembryonic Pregnancy: Definition, Diagnosis, and Management

An anembryonic pregnancy, previously known as a blighted ovum, is a specific type of early pregnancy loss (EPL) where a gestational sac develops without an embryo, diagnosed when the gestational sac measures 25 mm or larger without an embryo, or when there is absence of an embryo on serial ultrasound examinations obtained at discriminatory time intervals. 1

Diagnostic Criteria

• Defined by the Society of Radiologists in Ultrasound (SRU) as a gestational sac measuring 25 mm or larger without an embryo
• Alternatively diagnosed when serial ultrasound examinations show absence of an embryo development over appropriate time intervals
• Represents a specific subtype of early pregnancy loss (EPL)
• Transvaginal ultrasound is the primary diagnostic tool

Terminology Evolution

The terminology for this condition has evolved significantly in recent medical practice:

• "Blighted ovum" is now considered outdated terminology and should be avoided 1
• "Anembryonic pregnancy" is the preferred specific term 1
• More generally, this condition falls under the broader category of "diagnostic of EPL" (early pregnancy loss) 1, 2

Pathophysiology

An anembryonic pregnancy occurs when:

• Fertilization and implantation take place normally
• The gestational sac and placental tissue begin to develop
• The embryo either fails to develop or stops developing very early
• The pregnancy continues to produce hormones despite no viable embryo
• The gestational sac continues to grow despite embryonic absence

Clinical Presentation

Patients with an anembryonic pregnancy may present with:

• Amenorrhea and positive pregnancy test
• Vaginal bleeding (in some cases)
• Lower abdominal pain or cramping (in some cases)
• Pregnancy symptoms that may persist or diminish

Ultrasound Findings

Characteristic findings include:

• Gestational sac measuring ≥25 mm without an embryo 1
• Empty gestational sac that continues to grow on serial examinations
• Absence of yolk sac or embryonic pole within an appropriately sized sac
• Normal-appearing gestational sac with no embryonic structures

Management Approaches

Management options align with those for other types of early pregnancy loss:

• Expectant management: Waiting for natural expulsion of pregnancy tissue
• Medical management: Medication-induced expulsion (typically misoprostol)
• Surgical management: Dilation and curettage or vacuum aspiration 2

The choice between these approaches depends on:

• Patient preference
• Clinical circumstances (bleeding, infection risk)
• Emotional considerations
• Time constraints

Clinical Importance

Understanding anembryonic pregnancy is important because:

• It represents approximately 50% of first-trimester miscarriages
• Early and accurate diagnosis prevents unnecessary interventions
• Proper terminology helps reduce patient distress
• Appropriate counseling about future pregnancy outcomes is essential

Patient Communication

When discussing this diagnosis:

• Use the term "anembryonic pregnancy" or "early pregnancy loss" rather than "blighted ovum" 1
• Explain that this is a common occurrence (10-20% of clinically recognized pregnancies) 2
• Emphasize that it typically results from chromosomal abnormalities, not from anything the patient did
• Discuss management options and expected outcomes
• Provide emotional support and resources

Common Pitfalls to Avoid

• Premature diagnosis: Ensure gestational sac meets size criteria (≥25 mm) before making diagnosis 1
• Terminology errors: Avoid outdated terms like "blighted ovum" which can be distressing to patients 1
• Missing ectopic pregnancy: In rare cases, an anembryonic intrauterine pregnancy can coexist with an ectopic pregnancy (heterotopic pregnancy) 3
• Inadequate follow-up: If diagnosis is uncertain, follow-up ultrasound in 7-10 days is essential 2

Follow-up Care

• Confirm complete expulsion of pregnancy tissue regardless of management approach
• Monitor for complications (infection, excessive bleeding, retained tissue)
• Provide emotional support
• Discuss timing of future pregnancy attempts (typically can begin trying after one normal menstrual cycle)

Understanding anembryonic pregnancy as a specific form of early pregnancy loss helps guide appropriate management and patient counseling, with emphasis on using current terminology that is both medically accurate and sensitive to patient experiences.