ABSTRACT
The value of serum enzyme tests in these respects is maintained throughout pregnancy. However, normal pregnancy, particularly in its later stages, produces a pattern of changes in serum enzyme activities upon which pathological abnormalities are imposed, so that the interpretation of serum enzyme levels in pregnancy must take into account these physiological variations. The activities of several enzymes have been shown to be increased regularly in the serum or plasma of women during normal pregnancy. Heat-stable alkaline phosphatase is detectable in the serum of pregnant women between the 16th and 20th weeks of pregnancy and its amount increases progressively up to the onset of labor. The activities of several enzymes in serum have been shown to undergo marked increases in hepatobiliary diseases in which the flow of bile is impaired; the determination of one or more of these enzymes has become one of the most useful applications of diagnostic enzymology.
