Early detection of pregnancy-associated serum protein using antiserum to placental antigens.

Antisera against human placental proteins were developed in goats and rabbits, using immunoadjuvants and a prolonged injection schedule. The antisera were absorbed with normal serum proteins and then tested in immunodiffusion against normal and pregnancy sera. Two bands of precipitation due to pregnancy antigens were observed in pregnancy sera as early as 18 days after conception. Detection of these antigens has possibilities for application as an early pregnancy test.