## Clinical Context: Blighted Ovum & Gastrulation Failure A blighted ovum (anembryonic pregnancy) represents failure of the embryonic disc and primitive streak to form during the second and third weeks of gestation. The gestational sac develops, but the bilaminar disc and subsequent gastrulation do not occur, resulting in absence of the primitive streak, notochord, and axial structures. ### Why Repeat Ultrasound is the Next Step **Key Point:** In early pregnancy loss before 12–13 weeks, a single ultrasound showing no fetal pole or yolk sac is NOT diagnostic of miscarriage — it may represent: - Very early normal pregnancy (< 5 weeks by LMP) - Incorrect dating - Ectopic pregnancy - True blighted ovum **High-Yield:** ACOG and RCOG guidelines recommend **repeat transvaginal ultrasound in 7–14 days** before confirming diagnosis and offering intervention. This avoids unnecessary intervention in viable pregnancies. ### Management Algorithm ```mermaid flowchart TD A[Ultrasound: No fetal pole/yolk sac at 8 weeks]:::outcome --> B{hCG level and dating certain?}:::decision B -->|Uncertain dating| C[Repeat TVS in 1-2 weeks]:::action B -->|Certain, hCG low/plateauing| D[Confirm miscarriage]:::outcome C --> E{Fetal pole now visible?}:::decision E -->|Yes| F[Normal pregnancy, continue]:::action E -->|No| G[Confirm blighted ovum]:::outcome G --> H{Patient preference?}:::decision H -->|Expectant| I[Observe, monitor hCG]:::action H -->|Medical| J[Mifepristone + misoprostol]:::action H -->|Surgical| K[D&C or MVA]:::action ``` **Clinical Pearl:** The patient is asymptomatic with no bleeding — there is no urgency for immediate intervention. Confirmation prevents overtreatment of viable pregnancies. **Tip:** Remember the **"rule of 8"** — by 8 weeks, a normal pregnancy should show a fetal pole with cardiac activity. However, a single scan in early pregnancy is insufficient to diagnose loss; always repeat before counseling termination. 
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