Pyruvate kinase in human amniotic fluid--a new indicator of fetal maturity in late pregnancy.

During the second and third trimesters increasing activities of the glycolytic enzyme pyruvate kinase are to be found in human amniotic fluid. At term (37 to 42 weeks), a very steep rise in amniotic fluid pyruvate kinase can be noticed, which may serve as an additional prenatal indicator of fetal maturity. The presumable main sources of the enzyme in amniotic fluid are the epithelium cells of the skin, the respiratory tract and the amnion. In meconium stained amniotic fluid no pyruvate kinase activity is detectable. Addition of meconium to amniotic fluid samples with previously present pyruvate kinase activity leads to a disappearance of the enzyme activity.