Bovine placentomes were collected during late gestation, prepartum and immediately postpartum. Postpartum tissues were collected prior to fetal membrane separation. Maternal and fetal placentomal components each were examined for their ability to synthesize prostaglandins (PG's) from arachidonic acid (AA) and metabolize PGF2 alpha and PGE2 in vitro. Maternal placental PG synthesis was lower (P less than .05) than that for fetal placental tissue and was primarily PGF's. Fetal placental PG synthesis increased (P less than .05) prepartum and was primarily PGE's. Fetal placental PGE production predominated (P less than .05) postpartum if the fetal membranes were retained, while PGF production predominated (P less than .05) if the membranes were released. Maternal and fetal placental tissues were unable to convert PGE2 to PGF2 alpha (P greater than .05). Postpartum fetal placental tissue was able to convert PGF2 alpha to PGE2 (P less than .05) if the fetal membranes were retained but not if the membranes were released (P greater than .05). These results indicate that fetal placental synthesis of PGF's may be related to placental membrane separation. The shift in fetal placental PG production from PGE's to PGF's may be due to a cessation of the ability of released fetal tissue to convert PGF2 alpha to PGE2.