Changes in the concentration of total protein, albumin, ${alpha}_1-,{alpha}_2-,{eta}-,$ and ${gamma}-globulin$ in Serum from 138 healthy, normal pregnant woman were studied by the method of cellulose-acetate electrophoresis. 1. The concentration of total serum protein decreased gradually during the first 7 month, and showed a tendency to increase thereafter. 2. The concentration of serum albumin showed a steady continuous fall untill term. 3. During pregnancy,${alpha}_1$ and ${eta}-globulin$ value rose, ${gamma}-globulin$ value fell and ${alpha}_2-globulin$ value showed no significant change.