Presentation
Absent fetal cardiac pulsations on routine first trimester ultrasound scan (gestational age by LMD about 9 weeks).
Patient Data
Gravid uterus with large irregular gestational sac containing small non viable embryo. (There is evident discrepancy between the size of sac and that of the embryo).
The placenta is thickened, hyperreflective with multiple small cystic spaces inside and increased internal vascularity on Doppler scan.
Case Discussion
A molar pregnancy occurs when there is an extra set of paternal chromosomes in a fertilized egg. This error at the time of conception transforms normal placental tissue into a growing cystic mass
Partial hydatidiform mole has a triploid karyotype in which two of the three chromosomal complements are paternal (with a majority of 70% being XXY)
- Incidence is 2-3 times higher than a complete mole and occurs in 1 of 700 conceptions.
Most partial moles miscarry before 10-12 weeks. Risk of progression to persistent gestational trophoblastic disease is 2-4% and the lungs are most common site of metastasis. Risk of second molar pregnancy is 1.7%
Differential diagnosis:
Considerations on early ultrasound scans include:
- fetal demise with placental hydropic change: beta HCG levels are invariably low in this case
- twin pregnancy with one normal twin and one complete hydatidiform mole: the normal twin usually has its own normal placenta
- placental mesenchymal dysplasia.
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