Pregnancy-associated major basic protein in amniotic fluid.

The pregnancy-associated major basic protein, a protein elevated in the sera of all pregnant women, is virtually identical to the eosinophil granule major basic protein. To determine whether pregnancy-associated major basic protein is present in amniotic fluid, we examined samples from both early and late gestation by a double antibody radioimmunoassay. A total of 112 amniotic fluids were tested and all but three contained levels of pregnancy-associated major basic protein greater than 400 ng/ml. Amniotic fluid pregnancy-associated major basic protein antigenic activity was immunochemically identical to that of the eosinophil granule major basic protein and also had identical physicochemical properties such as heat stability and the need for reduction and alkylation. Although the majority of amniotic fluid samples (90 of 112) were obtained from healthy women with normal gestations, the remaining 21 amniotic fluid samples were from women with Rh sensitization and from one gestation complicated by intrauterine growth retardation.