Trophoblastic proliferation without fetus

Classic 2nd-trimester findings described as “Swiss cheese” or “cluster of grapes” endometrium

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  No fetus or embryo

  
  
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  Increased vascularity on color Doppler

  
  
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  Areas of hemorrhage common

1st-trimester appearance very different than seen later

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  Thickened, irregular endometrium

  
  
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  Appearance may mimic retained products of conception or anembryonic pregnancy

Ovarian theca lutein cysts in 50% of cases

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  Result from ovarian hyperstimulation due to ↑ hCG

  
  
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  Rare < 13 weeks

Invasive mole in 12-15%; choriocarcinoma in 5-8%

Placental hydropic degeneration

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  Hydropic change of developing placenta after pregnancy failure

  
  
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  hCG will be low rather than elevated

Triploidy (partial mole)

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  3 complete sets of chromosomes

  
  
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  Placenta is cystic when extra set is from father

  
  
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  Fetus is present but abnormal; severe growth restriction

Always evaluate with color Doppler, but be aware absence of flow does not mean it is not molar pregnancy

Evaluate interface with myometrium carefully looking for invasion

Must distinguish twin pregnancy with coexistent mole from triploidy

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  This will be dizygotic twin pregnancy with 1 normal fetus and 1 complete hydatidiform mole

  
  
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  Look for thick separating membrane (dichorionic)

Evaluate ovarian size and appearance

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  Theca lutein cysts may cause massive ovarian enlargement