Postpartum decline in serum concentration of placental proteins in an abdominal pregnancy.

The alpha and the beta forms of Schwangerschaftsprotein 1 (SP1) and chorionic gonadotrophin (hCG) were measured after delivery in an abdominal pregnancy with the placenta left in situ. All three proteins declined more slowly than after normal delivery; the half-lives ranging from 6.2-6.5 days. Traces of the proteins could still be detected in the maternal circulation 9 weeks after delivery. These findings are construed as further support for the belief that the placenta plays a major role in the synthesis of these proteins.