Pregnancy-associated alpha 2-macroglobulin - a new serum protein elevated in normal human pregnancy

A new pregnancy-associated serum protein has been isolated and characterised - pregnancy-associated alpha 2-macroglobulin (alpha 2-PAM). The native macromolecule has a molecular weight of 2.1 x 10(6) and a sedimentation coefficient of 19.6 S. This is comprised of 28 000 dalton subunits and contains 11% carbohydrate. alpha 2-PAM was found in normal male and female blood at a concentration of 25 micrograms/ml but no significant variation in this value was apparent in individuals followed over a 12 week period. The serum level can rise up to 16-fold during the first trimester of pregnancy and returns to normal levels within 8 weeks after delivery. Concentrations in contraceptive-steroid treated women, cord blood and breast milk were in the same range as normal adult sera while alpha 2-PAM could readily be detected in amniotic fluid at 8 micrograms/ml.