Immunochemical investigations on the problem of the pregnancy zone protein. XII. Serum concentrations of pregnancy-associated alpha-2-glycoprotein in diabetic pregnancy.

The concentration in serum of the pregnancy zone protein (PZ), a high molecular pregnancy-associated alpha 2-glycoprotein, increases during pregnancy, when oral contraceptives are taken and under certain pathological conditions. PZ is probably part of a multifactorial immunological defence system which prevents the premature rejection of the fetus and placenta which together may be regarded as an allograft. Normally, the PZ serum concentration begins to rise during the 6th-12th week of pregnancy and reaches its peak at about the 24th week. The mean values then remain stable and afterwards diminish slightly toward the end of the pregnancy. In contrast, the mean values in mothers with insulin-dependent diabetes mellitus continue to rise. Excessively high serum PZ concentrations are significantly more frequent among pregnant diabetic patients, especially where there is also rhesus D antigen incompatibility. No correlation was found between excessively high values and the risk features used for the Priscilla White classification. A few patients with progressive proliferative retinopathy even had unusually low values.