Pregnancy‐associated plasma protein A (PA‐A) in non‐pregnant subjects

A newly developed enzyme immunoassay technique was alied to the measurement of pregnancy‐associated plasma protein A (PA‐A) in the serum of women in the proliferative and luteal phases of the cycle, in hysterectomized and postmenopausal women and in the serum and seminal plasma of males. PA‐A was detected in some individuals in all the categories of women and in seminal plasma but not in male serum. It is surmised that there must be a source of PA‐A other than the placenta and that PA‐A may be a maternal protein whose biosynthesis is stimulated by pregnancy rather than a product peculiar to the trophoblast.