Prenatal diagnosis of a placental cyst: comparison of postnatal biochemical analyses of cyst fluid, amniotic fluid, cord serum, and maternal serum.

A 4 x 4 cm placental cyst was diagnosed prenatally by ultrasonography. At delivery, simultaneous samples of cyst fluid, amniotic fluid, cord blood, and maternal blood (collected 3 hours before delivery) were obtained. Biochemical measurements of cyst fluid, amniotic fluid, cord serum, and maternal serum suggest that the solutes of cyst fluid do not originate exclusively from a single source. In addition, X-cell synthesis and secretion into the cyst fluid may occur.