Changes in plasma proteins during pregnancy.

Changes in maternal plasma proteins during pregnancy are now well documented. These changes may be quantitative, as seen in the electrophoretically separated fractions of serum and in the various binding globulins; or they may be represented by the appearance of a protein which is present only in the serum of pregnant women. These include the placental isoenzyme of alkaline phosphatase, oxytocinase, human chorionic gonadotropin and the "pregnancy-associated plasma proteins." Other constituents, such as alpha-fetoprotein, salivary amylase, prolactin and the proteins of the "pregnancy zone," which are present in small quantities in non-pregnant women as well as in men, show a substantial increase in concentration in the maternal circulation during pregnancy. An important factor in the etiology of protein changes is the effect of hormones, especially estrogen, on the synthesis and degradation of these proteins. While certain quantitative changes such as those seen in hormone binding proteins may interfere with diagnostic procedures, a number of pregnancy-associated changes in protein composition of the maternal circulation may be used to follow the course of pregnancy by monitoring placental function as well as fetal maturity and well being.