Development of a Radioimmunoassay for Pregnancy-Associated Plasma Protein A and Establishment of Normal Levels in the First Trimester of Pregnancy

An accelerated double antibody method has been developed for the radioimmunoassay of pregnancy-associated plasma protein A (PAPP-A) in serum. The workable range for the assay was 0·04–1·8 mg/l of serum. PAPP-A levels were determined in single serum samples from 110 women with prospective normal pregnancies of between 7 and 14 weeks' gestation. The level of pregnancy specific β1 glycoprotein (SP1) was also measured in these samples and normal ranges for PAPP-A and SP1 were constructed from the results obtained.