Cortisol in Amniotic Fluid During Human Gestation

Cortisol was measured by specific radiotransinassay in 200 human amniotic fluids obtained throughout pregnancy. Correlation of amniotic fluid cortisol with umbilical cord cortisol (r = 0.69, P<0.01) was considerably better than that of amniotic fluid cortisol and maternal serum cortisol (r = 0.31, P<0.05). During gestation there was a rise in amniotic fluid cortisol from 5 ng/ml at 10 to 15 weeks to about 10 ng/ml from 25 to 35 weeks. An abrupt riseto 22 ng/ml occurred in the last week or two of pregnancy prior to the onset of labour. Values in infants with Rhdisease were within the normal range except in a few instances where very high levels were found just prior to death. These data support the concepts that the human fetus can respond to stress in utero and that a rise in cortisol is associated with the mechanism triggering normal labour.