Small for gestational age fetus with AC on the 10th centile and EFW on the 7th. No morphologic abnormality was seen, and the AFI and Dopplers were normal.
Directly caudal to the normal placental tissue, there is abnormal heterogeneous tissue with multiple cystic spaces and small amount of vascularity. It contacts the placenta at the margin but appears to be separate from it, and it wraps around the lower uterine cavity, covering the internal os. The interface between the normal placenta and abnormal tissue is shown in the second image stack.
The cervix is closed.
The appearance was highly unusual, and the differentials considered at this stage included uncommon conditions, including late-stage diagnosis of partial or concurrent molar pregnancy, partially hydropic placenta with placenta previa (though it would be exceedingly unlikely for a single placenta to have such varied appearances) or placental mesenchymal dysplasia.