Synonym: Partial mole

Definition: 69 chromosomes (instead of 46)

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  Most common is diandric triploidy (extra set is paternal)

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  Digynic triploidy if extra set is maternal

2 different appearances

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  Diandric triploidy

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    Large cystic placenta

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    Symmetric fetal growth restriction (FGR)

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    Ovaries enlarged with theca lutein cysts

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  Digynic triploidy

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    Normal or small placenta

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    Asymmetric FGR (large head, small body)

Multiple other anomalies common

Abnormal gestational sac in early 1st trimester

Abnormal anatomy at nuchal translucency (NT) screening

Twin molar pregnancy: Classic mole + normal fetus

Placental hydropic/edema from failed pregnancy

Placental mesenchymal dysplasia (can look identical)

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  Cystic placenta, associated with preeclampsia, FGR

Definitive diagnosis with placental biopsy or amniocentesis

Part of gestational trophoblastic disease spectrum

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  Variable hCG levels

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    High hCG associated with theca lutein ovarian cysts

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  Associated preeclampsia and placental abruption

Triploidy considered lethal diagnosis

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  Most with intrauterine fetal demise

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  Lethal in neonatal period if live birth

Look carefully for fetal anomalies when cysts seen in placenta, even at time of NT screening