Triploidy





KEY FACTS


Terminology





  • Synonym: Partial mole



  • Definition: 69 chromosomes (instead of 46)




    • Most common is diandric triploidy (extra set is paternal)



    • Digynic triploidy if extra set is maternal




Imaging





  • 2 different appearances




    • Diandric triploidy




      • Large cystic placenta



      • Symmetric fetal growth restriction (FGR)



      • Ovaries enlarged with theca lutein cysts




    • Digynic triploidy




      • Normal or small placenta



      • Asymmetric FGR (large head, small body)





  • Multiple other anomalies common



  • Abnormal gestational sac in early 1st trimester



  • Abnormal anatomy at nuchal translucency (NT) screening



Top Differential Diagnoses





  • Twin molar pregnancy: Classic mole + normal fetus



  • Placental hydropic/edema from failed pregnancy



  • Placental mesenchymal dysplasia (can look identical)




    • Cystic placenta, associated with preeclampsia, FGR




Clinical Issues





  • Definitive diagnosis with placental biopsy or amniocentesis



  • Part of gestational trophoblastic disease spectrum




    • Variable hCG levels




      • High hCG associated with theca lutein ovarian cysts




    • Associated preeclampsia and placental abruption




  • Triploidy considered lethal diagnosis




    • Most with intrauterine fetal demise



    • Lethal in neonatal period if live birth




Scanning Tips





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







Ultrasound-guided chorionic villus sampling is performed in this 13-week pregnancy with a thick cystic placenta . The needle tip is seen within the placenta. Noninvasive testing cannot reliably detect triploidy, and placental biopsy is necessary for accurate diagnosis.





Nov 10, 2024 | Posted by in ULTRASONOGRAPHY | Comments Off on Triploidy

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