Plasma Protein Synthesis in the Human Fetus and Placenta1

Electrophoretic studies of human fetal plasma have demonstrated a protein pattern in which all major fractions are present (1). The site of origin of these plasma proteins is not known. Presumably they may be synthesized by the mother and merely circulate in the fetus as the result of placental transfer, or they may be synthesized by the placenta or the fetus. The gamma globulin level is high at birth and falls during the first weeks of life (2). This led to the assumption that the gamma globulin found at