Antenatal sonographic detection of an unusual placental lake under the cord insertion

We detected an unusual placental lake under the membranes between the two lobes of a placenta bilobate with a turbulent blood flow in it. This was an extraordinary maternal lake: simply the accumulation of maternal blood inside the intervillous space in an area where villous structures were absent between the placental lobes. The lake reduced in size and became almost invisible during the Braxton Hicks contractions, and enlarged up to its previous dimensions at the end of contractions. This extraordinarily huge lake showed an interesting dynamic appearance on sonographic examination. Although it caused no complications during the course of the pregnancy it produced an obstetric hemorrhage, which took place during the second stage of the delivery. Pathologic examination confirmed the diagnosis of placenta bilobate. We present its interesting appearance and clinical outcome in this paper.