Studies on the concentration of pregnancy-associated plasma protein-A during normal and complicated pregnancy.

Pregnancy-associated plasma protein-A was assayed in the blood of 347 women during pregnancy, using a new primary standard of PAPP-A as reference. The protein was assayed by antibody-antigen crossed electrophoresis with the lower limit of confident assay being 9.5 micrograms PAPP-A/ml (13 pmol/ml). PAPP-A was first detected at 14 weeks of gestation; by term it had risen to within the range 20 to 320 micrograms/ml. There was an indication that pregnancies involving a male baby had higher PAPP-A levels in blood than did those involving female babies. In 51 blood samples from 30 patients with gestational diabetes (taken between 28 weeks of pregnancy and term) there was no significant alteration in PAPP-A values compared with controls. In 35 blood samples from 15 patients with insulin-dependent diabetes, levels of PAPP-A were significantly lower than in controls or in gestational diabetes. In 43 blood samples from 35 patients with babies affected with intrauterine growth retardation (between 28 weeks and term), there was no significant difference in PAPP-A levels compared with controls. The effect of insulin on the blood levels of PAPP-A suggests that the concentration of PAPP-A is capable of altering significantly in response to certain physiological changes associated with the control of carbohydrate metabolism.