Placental Snowstorm Appearance in the First Trimester: Expert Assessment of the Fetal Anatomy Does Matter

Snowstorm appearance of the placenta warrants a differential diagnosis among placental mesenchymal dysplasia, partial molar pregnancy and dichorionic twin pregnancy with a complete mole in one sac. Albeit sharing the "unusual" appearance of the placenta, the three conditions differ in terms of management and prognosis as well as serum biochemistry and association with structural and genetic fetal anomalies. In our experience, the expert sonographic assessment of fetal anatomy best performs in differentiating the conditions as early as the first trimester. We present a case in which placental assessment and serial biochemistry were suspicious for placental mesenchymal dysplasia, but the early detection of a cono-truncal cardiac abnormality shifted the diagnostic hypothesis toward partial molar pregnancy, which was confirmed by an invasive procedure.