Studies on the half-life of Schwangerschaftsprotein 1 (SP1).

Schwangerschaftsprotein 1 (SP1) was measured in 10 women at intervals after delivery of the placenta. SP1 alpha decreased more sharply than SP1 beta and showed evidence of a two-compartmental distribution in the mother. Trace amounts of both proteins could still be detected 5 weeks after delivery. It is concluded that the findings support the view that the two proteins are separate biological entities and that there is a possibility that SP1 beta is generated from SP1 alpha in the maternal compartment.