KEY FACTS
Terminology
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Synonym: Partial mole
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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
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Imaging
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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)
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Multiple other anomalies common
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Abnormal gestational sac in early 1st trimester
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Abnormal anatomy at nuchal translucency (NT) screening
Top Differential Diagnoses
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Twin molar pregnancy: Classic mole + normal fetus
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Placental hydropic/edema from failed pregnancy
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Placental mesenchymal dysplasia (can look identical)
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Cystic placenta, associated with preeclampsia, FGR
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Clinical Issues
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Definitive diagnosis with placental biopsy or amniocentesis
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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
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Triploidy considered lethal diagnosis
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Most with intrauterine fetal demise
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Lethal in neonatal period if live birth
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Scanning Tips
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Look carefully for fetal anomalies when cysts seen in placenta, even at time of NT screening