Changes of biochemical constituents in bovine fetal fluids with gestational age.

Serum, amniotic fluid, allantoic fluid, stomach contents, and urine were taken from 141 bovine fetuses 120 to 245 days old. The concentrations of the biochemical constituents were examined in tests to ascertain systematic changes with increasing crown-rump length, i.e., gestational age. As the crown-rump length increased, glucose concentrations decreased in allantoic fluid, amniotic fluid, and stomach contents; creatinine and uric acid concentrations increased in serum, allantoic fluid, and stomach contents; thyroxine concentrations increased in serum and allantoic fluid; potassium decreased in amniotic fluid and stomach contents; and total iron-binding capacity increased in amniotic fluid. The data in the present report can be used to identify the fetal fluid obtained by amniocentesis, to estimate the age of the fetus, and to aid the diagnosis of nutritional or infective processes that might affect the fetus.